As of the census² of 2000, there were 119,341 people, 41,373 households, and 33,305 families residing in the county. The population density was 143/km² (370/mi²). There were 43,166 housing units at an average density of 52/km² (134/mi²). The racial makeup of the county was 81.38% White, 14.68% Black or African American, 0.23% Native American, 1.76% Asian, 0.04% Pacific Islander, 0.79% from other races, and 1.13% from two or more races. 2.26% of the population were Hispanic or Latino of any race.

There were 41,373 households out of which 42.90% had children under the age of 18 living with them, 66.40% were married couples living together, 10.30% had a female householder with no husband present, and 19.50% were non-families. 15.40% of all households were made up of individuals and 4.00% had someone living alone who was 65 years of age or older. The average household size was 2.87 and the average family size was 3.19.

The median income for a household in the county was $57,309, and the median income for a family was $61,607. Males had a median income of $41,449 versus $29,211 for females. The per capita income for the county was $22,945. About 3.70% of families and 4.90% of the population were below the poverty line, including 5.50% of those under age 18 and 7.80% of those age 65 or over.

Neighboring areas include the following: DeKalb County, Rockdale County, Newton County, Butts County, Spalding County, and Clayton County. The cities and towns of Henry County are Blacksville, Hampton, Locust Grove, McDonough, Stockbridge, Ola, Luella, and Flippen.