As of the census of 2000, there were 18,974 people, 6,696 households, and 4,955 families residing in the county. The population density was 72 people per square mile (28/km²). There were 7,368 housing units at an average density of 28 per square mile (11/km²). The racial makeup of the county was 51.83% White, 41.21% Black or African American, 0.30% Native American, 0.09% Asian, 0.01% Pacific Islander, 5.75% from other races, and 0.80% from two or more races. 7.96% of the population were Hispanic or Latino of any race.
There were 6,696 households out of which 34.30% had children under the age of 18 living with them, 52.10% were married couples living together, 17.30% had a female householder with no husband present, and 26.00% were non-families. 22.60% of all households were made up of individuals and 10.00% had someone living alone who was 65 years of age or older. The average household size was 2.65 and the average family size was 3.09.
In the county the population was spread out with 25.30% under the age of 18, 9.40% from 18 to 24, 30.90% from 25 to 44, 22.30% from 45 to 64, and 12.10% who were 65 years of age or older. The median age was 36 years. For every 100 females there were 105.70 males. For every 100 females age 18 and over, there were 103.90 males.
The median income for a household in the county was $32,074, and the median income for a family was $36,419. Males had a median income of $27,048 versus $21,351 for females. The per capita income for the county was $15,452. About 16.00% of families and 20.20% of the population were below the poverty line, including 28.30% of those under age 18 and 20.50% of those age 65 or over.
The closest airport to Greene County is Pitt-Greenville Airport (IATA: PGV, ICAO: KPGV, FAA LID: PGV) with service to Charlotte Douglas International Airport, although most residents use Raleigh-Durham International Airport for domestic and international travel.
The major highways that run through the county are US 264 and US 13. Other highways include US 258, NC 903, NC58, NC 102 and NC 91. The closest interstate is I-95, located northwest of the county in Wilson.