Japan competed at the 1984 Summer Olympics in Los Angeles, United States. Japan returned to the Games after participating in the American-led boycott of the 1980 Summer Olympics. 226 competitors, 174 men and 52 women, took part in 147 events in 22 sports.
Medalists
| width=78% align=left valign=top |
{| class="wikitable sortable" style="font-size:95%"
|-
! Medal
! Name
! Sport
! Event
! Date
|-
| || Kōji Gushiken || Gymnastics || Men's individual all-around || August 2
|-
| || Takeo Kamachi || Shooting || Men's rapid fire pistol || August 2
|-
| || Atsuji Miyahara || Wrestling || Men's Greco-Roman flyweight || August 2
|-
| || Shinji Morisue || Gymnastics || Men's horizontal bar || August 4
|-
| || Kōji Gushiken || Gymnastics || Men's rings || August 4
|-
| || Shinji Hosokawa || Judo || Men extra lightweight || August 4
|-
| || Yoshiyuki Matsuoka || Judo || Men half lightweight || August 5
|-
| || Hitoshi Saito || Judo || Men heavyweight || August 10
|-
| || Yasuhiro Yamashita || Judo || Men's open category || August 11
|-
| || Hideaki Tomiyama || Wrestling || Men's freestyle bantamweight || August 11
|-
| || Masaki Eto || Wrestling || Men's Greco-Roman bantamweight || August 3
|-
| || Nobuyuki Kajitani || Gymnastics || Men's parallel bars || August 4
|-
| || Kōji Gushiken || Gymnastics || Men's vault || August 4
|-
| || Shinji Morisue || Gymnastics || Men's vault || August 4
|-
| || Takashi Irie || Wrestling || Men's freestyle light flyweight || August 9
|-
| || Kosei Akaishi || Wrestling || Men's freestyle featherweight || August 9
|-
| || Akira Ota || Wrestling || Men's freestyle light heavyweight || August 9
|-
| || Hideyuki Nagashima || Wrestling || Men's freestyle middleweight || August 11
|-
| || Kazushito Manabe || Weightlifting || Men's flyweight || July 29
|-
| || Masahiro Kotaka || Weightlifting || Men's bantamweight || July 30
|-
| || Kōji Gushiken<br/>Noritoshi Hirata<br/>Nobuyuki Kajitani<br/>Shinji Morisue<br/>Koji Sotomura<br/>Kyoji Yamawaki || Gymnastics || Men's team all-around || July 31
|-
| || Ikuzo Saito || Wrestling || Men's Greco-Roman light flyweight || August 1
|-
| || Tsutomu Sakamoto || Cycling || Men's sprint || August 3
|-
| || Koji Sotomura || Gymnastics || Men's floor || August 4
|-
| || Kōji Gushiken || Gymnastics || Men's horizontal bar || August 4
|-
| || Ryoji Isaoka || Weightlifting || Men's light heavyweight || August 4
|-
| || Yumi Egami<br/>Norie Hiro<br/>Miyoko Hirose<br/>Kyoko Ishida<br/>Yoko Kagabu<br/>Yuko Mitsuya<br/>Keiko Miyajima<br/>Kimie Morita<br/>Kumi Nakada<br/>Emiko Odaka<br/>Sachiko Otani<br/>Kayoko Sugiyama || Volleyball || Women's tournament || August 7
|-
| || Seiki Nose || Judo || Men's middleweight || August 8
|-
| || Saeko Kimura<br/>Miwako Motoyoshi || Artistic swimming || Women's duet || August 9
|-
| || Yuji Takada || Wrestling || Men's freestyle light flyweight || August 10
|-
| || Hiroshi Yamamoto || Archery || Men's individual || August 11
|-
| || Miwako Motoyoshi || Artistic swimming || Women's solo || August 12
|}
| width=22% align=left valign=top |
{| class=wikitable style="font-size:95%; float:right"
|-
!colspan=7|Medals by sport
|-align=center
|Sport
| bgcolor=f7f6a8 |
| bgcolor=dce5e5 |
| bgcolor=ffdab9 |
|Total
|-align=center
|Judo
| style="background:#F7F6A8;"| 4
| style="background:#DCE5E5;"| 0
| style="background:#FFDAB9;"| 1
|5
|-align=center
|Gymnastics
| style="background:#F7F6A8;"| 3
| style="background:#DCE5E5;"| 3
| style="background:#FFDAB9;"| 3
|9
|-align=center
|Wrestling
| style="background:#F7F6A8;"| 2
| style="background:#DCE5E5;"| 5
| style="background:#FFDAB9;"| 2
|9
|-align=center
|Shooting
| style="background:#F7F6A8;"| 1
| style="background:#DCE5E5;"| 0
| style="background:#FFDAB9;"| 0
|1
|-align=center
|Weightlifting
| style="background:#F7F6A8;"| 0
| style="background:#DCE5E5;"| 0
| style="background:#FFDAB9;"| 3
|3
|-align=center
|Artistic swimming
| style="background:#F7F6A8;"| 0
| style="background:#DCE5E5;"| 0
| style="background:#FFDAB9;"| 2
|2
|-align=center
|Archery
| style="background:#F7F6A8;"| 0
| style="background:#DCE5E5;"| 0
| style="background:#FFDAB9;"| 1
|1
|-align=center
|Cycling
| style="background:#F7F6A8;"| 0
| style="background:#DCE5E5;"| 0
| style="background:#FFDAB9;"| 1
|1
|-align=center
|Volleyball
| style="background:#F7F6A8;"| 0
| style="background:#DCE5E5;"| 0
| style="background:#FFDAB9;"| 1
|1
|- align=center
! Total
!style="background:gold"| 10
!style="background:silver"| 8
!style="background:#c96"| 14
! 32
|}
Archery
In their third Olympic archery competition, Japan won a bronze medal in the men's division as well as having a fourth place competitor in each division.
Women's Individual Competition:
- Hiroko Ishizu – 2525 points (4th place)
- Minako Hokari – 2481 points (10th place)
Men's Individual Competition:
- Hiroshi Yamamoto – 2563 points (Bronze Medal)
- Takayoshi Matsushita – 2552 points (4th place)
- Ichiro Shimamura – 2312 points (52nd place)
Athletics
Men's 400 metres
- Susumu Takana
:* Heat — 46.26
:* Quarterfinals — 45.91
:* Semifinals — 45.88 (→ did not advance)
Men's 10,000 metres
- Yutaka Kanai
:* Qualifying Heat — 28:14.67
:* Final — 28:27.06 (→ 7th place)
- Masanari Shintaku
:* Qualifying Heat — 28:24.30
:* Final — 28:55.54 (→ 16th place)
Men's Marathon
- Takeshi So
:* Final — 2:10:55 (→ 4th place)
- Toshihiko Seko
:* Final — 2:14:13 (→ 14th place)
- Shigeru So
:* Final — 2:14:38 (→ 17th place)
Men's Long Jump
- Junichi Usui
:* Qualification — 8.02m
:* Final — 7.87m (→ 7th place)
Men's High Jump
- Takao Sakamoto
:* Qualification — 2.21m (→ did not advance)
Men's Javelin Throw
- Masami Yoshida
:* Qualification — 81.42m
:* Final — 81.98m (→ 5th place)
- Kazuhiro Mizoguchi
:* Qualification — 74.82m (→ did not advance, 20th place)
Men's Hammer Throw
- Shigenobu Murofushi
:* Qualification — 70.92m (→ did not advance)
Men's Pole Vault
- Tomomi Takahashi
:* Qualifying Round — 5.30m
:* Final — no mark (→ no ranking)
Women's Marathon
- Nanae Sasaki
:* Final — 2:37:04 (→ 19th place)
- Akemi Masuda
:* Final — did not finish (→ no ranking)
Women's High Jump
- Hisayo Fukumitsu
:* Qualification — 1.87m (→ did not advance, 17th place)
- Megumi Sato
:* Qualification — 1.84m (→ did not advance, 18th place)
Women's Javelin Throw
- Emi Matsui
:* Qualification — 57.72m (→ did not advance)
- Minori Mori
:* Qualification — 56.60m (→ did not advance)
Boxing
Men's Light Flyweight (– 48 kg)
- Mamoru Kuroiwa
- First Round — Bye
- Second Round — Defeated Francisco Tejedor (COL), 4:1
- Quarterfinals — Lost to Keith Mwila (KEN), 0:5
Men's Bantamweight (– 54 kg)
- Hiroaki Takami
- First Round — Bye
- Second Round — Defeated Gamaleldin El-Koumy (EGY), 4:1
- Third Round — Lost to Dale Walters (CAN), 0:5
Canoeing
Cycling
Nine cyclists, eight men and one woman, represented Japan in 1984. Tsutomu Sakamoto won a bronze medal in the sprint event.
;Men's individual road race
- Matsuyoshi Takahashi — 45th place
;Sprint
- Tsutomu Sakamoto
- Katsuo Nakatake
;1000m time trial
- Tsutomu Sakamoto
;Team pursuit
- Akio Kuwazawa
- Harumitsu Okada
- Mitsugi Sarudate
- Yoshihiro Tsumuraya
;Points race
- Akio Kuwazawa
- Hitoshi Sato
;Women's individual road race
- Wakako Abe — 40th place
Diving
Men's 3m Springboard
- Isao Yamagishi
:* Preliminary Round — 427.14 (→ did not advance, 25th place)
Equestrianism
Fencing
Nine fencers, five men and four women, represented Japan in 1984.
;Men's foil
- Kenichi Umezawa
- Nobuyuki Azuma
- Tadashi Shimokawa
;Men's team foil
- Nobuyuki Azuma, Yoshihiko Kanatsu, Hidehachi Koyasu, Tadashi Shimokawa, Kenichi Umezawa
;Women's foil
- Azusa Oikawa
- Mieko Miyahara
- Miyuki Maekawa
;Women's team foil
- Mieko Miyahara, Azusa Oikawa, Miyuki Maekawa, Tomoko Oka
Gymnastics
Handball
;Men's Team Competition
- Preliminary Round (Group A)
:*Lost to Yugoslavia (15:32)
:*Lost to Romania (22:28)
:*Lost to Iceland (17:21)
:*Lost to Switzerland (13:20)
:*Defeated Algeria (17:16)
- Classification Match
:*9th/10th place: Lost to United States (16:24) → 10th place
- Team Roster
:*Seimei Gamo
:*Takashi Ikenoue
:*Yasou Ikona
:*Hidetada Ito
:*Koji Matsui
:*Mitsuaki Nakamoto
:*Kiyoshi Nishiyama
:*Takahiro Ohata
:*Nobuo Sasaki
:*Kenzo Seki
:*Yoshihiro Shiga
:*Katsutoshi Taguchi
:*Seiichi Takamura
:*Yukihiko Uemura
:*Shinji Yamamoto
Judo
Modern pentathlon
Three male pentathletes represented Japan in 1984.
;Individual
- Shoji Uchida
- Hiroyuki Kawazoe
- Daizou Araki
;Team
- Shoji Uchida
- Hiroyuki Kawazoe
- Daizou Araki
Rhythmic gymnastics
Rowing
Sailing
Shooting
;Men
{| class="wikitable" style="font-size:90%"
!rowspan="2"|Athlete
!rowspan="2"|Event
!colspan=2|Final
|-style="font-size:95%"
!Points
!Rank
|-align=center
|align=left|Hiroyuki Akatsuka
|align=left rowspan=1|25 m rapid fire pistol
|583
|23
|-align=center
|align=left|Norito Chosa
|align=left|50 m rifle, prone
|585
|43
|-align=center
|align=left|Chikafumi Hirai
|align=left rowspan=1|50 m pistol
|551
|18
|-align=center
|align=left|Takeo Kamachi
|align=left rowspan=1|25 m rapid fire pistol
|595
|16x16px
|-align=center
|align=left rowspan=2|Ryohei Koba
|align=left |50 m rifle, three positions
|1137
|25
|-align=center
|align=left|10 m air rifle
|578
|18
|-align=center
|align=left rowspan=1|Kaoru Matsuo
|align=left |50 m rifle, three positions
|1125
|35
|-align=center
|align=left|Hiroyuki Nakajo
|align=left|50 m rifle, prone
|591
|17
|-align=center
|align=left|Shigetoshi Tashiro
|align=left rowspan=1|50 m pistol
|540
|29
|}
;Women
{| class="wikitable" style="font-size:90%"
!rowspan="2"|Athlete
!rowspan="2"|Event
!colspan=2|Final
|-style="font-size:95%"
!Points
!Rank
|-align=center
|align=left|Keiko Hirakawa
|align=left rowspan=1|25 m pistol
|564
|23
|-align=center
|align=left rowspan=2|Noriko Kosai
|align=left |50 m rifle, three positions
|568
|11
|-align=center
|align=left|10 m air rifle
|383
|10
|-align=center
|align=left|Atsuko Sugimoto
|align=left rowspan=1|25 m pistol
|564
|23
|}
;Open
{| class="wikitable" style="font-size:90%"
!rowspan="2"|Athlete
!rowspan="2"|Event
!colspan=2|Final
|-style="font-size:95%"
!Points
!Rank
|-align=center
|align=left|Eigen Hayashi
|align=left rowspan=1|Skeet
|184
|41
|-align=center
|align=left|Motoharu Hirano
|align=left rowspan=1|Trap
|186
|11
|-align=center
|align=left|Mikio Itakura
|align=left rowspan=1|Skeet
|192
|13
|-align=center
|align=left|Kazumi Watanabe
|align=left rowspan=1|Trap
|186
|13
|}
Swimming
Men's 100m Freestyle
- Shigeo Ogata
:* Heat — 52.96 (→ did not advance, 33rd place)
- Satoshi Sumida
:* Heat — 53.83 (→ did not advance, 39th place)
Men's 200m Freestyle
- Hiroshi Sakamoto
:* Heat — 1:54.71 (→ did not advance, 26th place)
- Shigeo Ogata
:* Heat — 1:55.97 (→ did not advance, 33rd place)
Men's 400m Freestyle
- Shigeo Ogata
:* Heat — 4:02.97 (→ did not advance, 22nd place)
- Keisuke Okuno
:* Heat — 4:06.31 (→ did not advance, 27th place)
Men's 100m Backstroke
- Daichi Suzuki
:* Heat — 58.37
:* B-Final — 58.30 (→ 11th place)
Men's 200m Backstroke
- Daichi Suzuki
:* Heat — 2:06.24
:* B-Final — 2:06.02 (→ 16th place)
Men's 100m Breaststroke
- Shigehiro Takahashi
:* Heat — 1:04.71
:* B-Final — 1:04.41 (→ 10th place)
- Kenji Watanabe
:* Heat — 1:06.10 (→ did not advance, 9th place)
Men's 200m Breaststroke
- Shigehiro Takahashi
:* Heat — 2:19.98
:* B-Final — 2:20.93 (→ 12th place)
- Kenji Watanabe
:* Heat — 2:22.33
:* B-Final — 2:22.29 (→ 15th place)
Men's 100m Butterfly
- Taihei Saka
:* Heat — 56.40 (→ did not advance, 21st place)
- Shudo Kawawa
:* Heat — 56.52 (→ did not advance, 23rd place)
Men's 200m Butterfly
- Taihei Saka
:* Heat — 2:00.66
:* B-Final — 2:00.31 (→ 9th place)
- Shudo Kawawa
:* Heat — 2:03.07 (→ did not advance, 18th place)
Men's 200m Individual Medley
- Shinji Ito
:* Heat — 2:07.76
:* B-Final — 2:06.07 (→ 10th place)
Men's 400m Individual Medley
- Shinji Ito
:* Heat — 4:30.52
:* B-Final — 4:29.76 (→ 13th place)
Men's 4 × 100 m Freestyle Relay
- Hiroshi Sakamoto, Shigeo Ogata, Taihei Saka, and Satoshi Sumida
:* Heat — 3:30.45 (→ did not advance, 13th place)
Men's 4 × 200 m Freestyle Relay
- Taihei Saka, Hiroshi Sakamoto, Keisuke Okuno, and Shigeo Ogata
:* Heat — DSQ (→ did not advance, no ranking)
Men's 4 × 100 m Medley Relay
- Daichi Suzuki, Shigehiro Takahashi, Taihei Saka, and Hiroshi Sakamoto
:* Heat — 3:50.14
:* Final — DSQ (→ no ranking)
<br>
Women's 100m Freestyle
- Kaori Yanase
:* Heat — 58.47 (→ did not advance, 17th place)
- Chikako Nakamori
:* Heat — 59.00 (→ did not advance, 21st place)
Women's 200m Freestyle
- Chikako Nakamori
:* Heat — 2:03.94
:* B-Final — 2:04.11 (→ 13th place)
- Kaori Yanase
:* Heat — 2:04.38
:* B-Final — 2:05.24 (→ 16th place)
Women's 400m Freestyle
- Chikako Nakamori
:* Heat — 4:20.13
:* B-Final — 4:20.18 (→ 14th place)
- Junko Sakurai
:* Heat — 4:28.68 (→ did not advance, 19th place)
Women's 800m Freestyle
- Junko Sakurai
:* Heat — 9:13.27 (→ did not advance, 18th place)
Women's 4 × 100 m Freestyle Relay
- Junko Sakurai, Chikako Nakamori, Miki Saito, and Kaori Yanase
:* Heat — 3:54.68 (→ did not advance)
Women's 4 × 100 m Medley Relay
- Naomi Sekido, Hiroko Nagasaki, Naoko Kume, and Kaori Yanase
:* Heat — 4:17.59
:* Final — DSQ (→ no ranking)
Women's 100m Backstroke
- Naomi Sekido
:* Heat — 1:05.60 (→ did not advance, 18th place)
- Nozomi Sunouchi
:* Heat — 1:07.23 (→ did not advance, 23rd place)
Women's 200m Backstroke
- Naomi Sekido
:* Heat — 2:18.52
:* B-Final — 2:18.87 (→ 14th place)
- Nozomi Sunouchi
:* Heat — 2:25.05 (→ did not advance, 22nd place)
Women's 200m Butterfly
- Naoko Kume
:* Heat — 2:13.31
:* Final — 2:12.57 (→ 6th place)
- Kiyomi Takahashi
:* Heat — 2:14.37
:* B-Final — 2:16.27 (→ 12th place)
Women's 200m Individual Medley
- Hideka Koshimizu
:* Heat — 2:23.38
:* B-Final — 2:22.81 (→ 15th place)
Women's 400m Individual Medley
- Hideka Koshimizu
:* Heat — 4:59.18
:* B-Final — 4:58.02 (→ 14th place)
Synchronized swimming
Volleyball
;Men's Team Competition
- Preliminary Round (Group B)
:* Defeated China (3-0)
:* Defeated Italy (3-2)
:* Defeated Egypt (3-0)
:* Lost to Canada (0-3)
- Classification Matches
:* 5th/8th place: Lost to Argentina (1-3)
:* 7th/8th place: Defeated China (3-0) → 7th place
- Team Roster
:* Koshi Sobu
:* Eiji Shimomura
:* Kazuya Mitake
:* Eizaburo Mitsuhashi
:* Hiroaki Okuno
:* Yasushi Furukawa
:* Shuji Yamada
:* Mikiyasu Tanaka
:* Kimio Sugimoto
:* Minoru Iwata
:* Akihiro Iwashima
:* Shunichi Kawai
;Women's Team Competition
- Preliminary Round (Group A)
:* Defeated South Korea (3-1)
:* Defeated Peru (3-0)
:* Defeated Canada (3-0)
- Semi Finals
:* Lost to China (0-3)
- Bronze Medal Match
:* Defeated United States (3-1) → Image:Med 3.png Bronze Medal
- Team Roster
:* Yumi Egami
:* Kimie Morita
:* Yuko Mitsuya
:* Miyoko Hirose
:* Kyoko Ishida
:* Yoko Kagabu
:* Norie Hiro
:* Kayoko Sugiiyama
:* Sachiko Otani
:* Keiko Miyajima
:* Emiko Odaka
:* Kumie Nakada
Water polo
;Men's Team Competition
- Preliminary Round (Group C)
:* Lost to Italy (5-15)
:* Lost to West Germany (8-15)
:* Lost to Australia (2-15)
- Final Round (Group E)
:* Lost to China (4-10)
:* Lost to Greece (7-14)
:* Lost to Canada (5-8)
:* Defeated Brazil (9-8) → 11th place
- Team Roster
:* Etsuji Fujita
:* Yoshifumi Saito
:* Koshi Fujimori
:* Shingo Kai
:* Narihito Taima
:* Daisuke Houki
:* Toshio Fukumoto
:* Toshiyuki Miyahara
:* Hisayoshi Nagata
:* Koji Wakayoshi
:* Hisaharu Saito
:* Shinji Yamasaki
:* Asami Oura