As of the census of 2000, there were 10,117 people, 3,565 households, and 2,506 families residing in the county. The population density was 25 people per square mile (10/km²). There were 3,923 housing units at an average density of 10 per square mile (4/km²). The racial makeup of the county was 30.47% White, 68.62% Black or African American, 0.13% Native American, 0.17% Asian, 0.01% Pacific Islander, 0.08% from other races, and 0.52% from two or more races. 0.54% of the population were Hispanic or Latino of any race.
There were 3,565 households out of which 34.40% had children under the age of 18 living with them, 37.60% were married couples living together, 26.80% had a female householder with no husband present, and 29.70% were non-families. 26.90% of all households were made up of individuals and 12.30% had someone living alone who was 65 years of age or older. The average household size was 2.80 and the average family size was 3.42.
In the county the population was spread out with 32.00% under the age of 18, 9.60% from 18 to 24, 25.70% from 25 to 44, 19.50% from 45 to 64, and 13.20% who were 65 years of age or older. The median age was 32 years. For every 100 females there were 86.50 males. For every 100 females age 18 and over, there were 79.30 males.
The median income for a household in the county was $20,636, and the median income for a family was $25,394. Males had a median income of $23,571 versus $16,993 for females. The per capita income for the county was $10,817. About 28.60% of families and 33.10% of the population were below the poverty line, including 43.10% of those under age 18 and 30.60% of those age 65 or over.
Quitman County has the fifth lowest per capita income in Mississippi and the 51st lowest in the United States.