As of the census of 2000, there were 19,788 people, 7,978 households, and 5,305 families residing in the city. The population density was 1,775.2 people per square mile (685.2/km²). There were 8,515 housing units at an average density of 763.9/sq mi (294.9/km²). The racial makeup of the city was 69.63% White, 23.91% African American, 0.45% Native American, 0.83% Asian, 3.83% from other races, and 1.35% from two or more races. Hispanic or Latino of any race were 6.93% of the population.
There were 7,978 households out of which 31.8% had children under the age of 18 living with them, 44.2% were married couples living together, 17.1% had a female householder with no husband present, and 33.5% were non-families. 28.6% of all households were made up of individuals and 10.9% had someone living alone who was 65 years of age or older. The average household size was 2.43 and the average family size was 2.96.
In the city the population was spread out with 25.5% under the age of 18, 9.0% from 18 to 24, 31.2% from 25 to 44, 20.0% from 45 to 64, and 14.3% who were 65 years of age or older. The median age was 34 years. For every 100 females there were 90.0 males. For every 100 females age 18 and over, there were 85.6 males.
The median income for a household in the city was $30,972, and the median income for a family was $35,933. Males had a median income of $27,479 versus $20,968 for females. The per capita income for the city was $16,045. About 11.8% of families and 16.2% of the population were below the poverty line, including 23.5% of those under age 18 and 16.4% of those age 65 or over.
Thomasville's population has grown much faster than the rest of North Carolina and the United States. The U.S. Census Bureau estimates that as of 2005 Thomasville's population reached 25,872, an annual average growth of over 6% from 2000. North Carolina grew at an average rate of 1.6%, and the United States grew at an average rate of 1%.