As of the census of 2000, there were 3,244 people, 1,085 households, and 864 families residing in the town. The population density was . There were 1,117 housing units at an average density of . The racial makeup of the town was 96.02% White, 2.37% African American, 0.18% Native American, 0.86% Asian, 0.06% Pacific Islander, 0.03% from other races, and 0.46% from two or more races. Hispanic or Latino of any race were 0.65% of the population.
There were 1,085 households, out of which 36.5% had children under the age of 18 living with them, 69% were married couples living together, 7.5% had a female householder with no husband present, and 20.3% were non-families. 16.8% of all households were made up of individuals, and 10% had someone living alone who was 65 years of age or older. The average household size was 2.75 and the average family size was 3.1.
In the town, the population was spread out, with 27.1% under the age of 18, 6.7% from 18 to 24, 25.8% from 25 to 44, 24.2% from 45 to 64, and 16.2% who were 65 years of age or older. The median age was 39 years. For every 100 females, there were 99.8 males. For every 100 females age 18 and over, there were 97 males.
The median income for a household in the town was $50,282, and the median income for a family was $57,009. Males had a median income of $37,663 versus $24,479 for females. The per capita income for the town was $19,593. 4.9% of the population and 3.7% of families were below the poverty line. 6% of those under the age of 18 and 4.7% of those 65 and older were living below the poverty line.
Communities and locations in Sennett
- McMasters Corners – A location on NY-34, west of Sennett village.
- Sennett ( once "Fellows Corners") – The hamlet of Sennett is located on NY-5, northeast of Auburn.
- Wicks Corners – A hamlet by the eastern town line, east of Auburn.
- Sennett Federated Church - A central landmark built in 1829 in the hamlet of Sennett that remains in use, located north of NY-5 at the corner of Turnpike Rd and Weedsport-Sennett Rd