The Village of Mannsville is in the southeast part of the town and is south of Watertown.
As of the census of 2000, there were 400 people, 143 households, and 106 families residing in the village. The population density was 434.6 people per square mile (167.9/km²). There were 168 housing units at an average density of 182.5/sq mi (70.5/km²). The racial makeup of the village was 99.25% White, 0.25% Native American, 0.25% Asian, and 0.25% from two or more races. Hispanic or Latino of any race were 0.50% of the population.
There were 143 households out of which 42.7% had children under the age of 18 living with them, 54.5% were married couples living together, 15.4% had a female householder with no husband present, and 25.2% were non-families. 18.2% of all households were made up of individuals and 9.1% had someone living alone who was 65 years of age or older. The average household size was 2.71 and the average family size was 3.07.
In the village the population was spread out with 28.8% under the age of 18, 7.3% from 18 to 24, 30.8% from 25 to 44, 18.0% from 45 to 64, and 15.3% who were 65 years of age or older. The median age was 36 years. For every 100 females there were 89.6 males. For every 100 females age 18 and over, there were 85.1 males.
The median income for a household in the village was $47,574, and the median income for a family was $48,182. Males had a median income of $29,545 versus $20,625 for females. The per capita income for the village was $16,768. About 13.6% of families and 15.7% of the population were below the poverty line, including 24.0% of those under age 18 and 4.5% of those age 65 or over.