As of the Census of 2000, there were 155,554 people, 65,499 households, and 39,626 families residing in the city. The population density was 1,150.5 people per square mile (444.2/km²). There were 72,108 housing units at an average density of 533.3/sq mi (205.9/km²). The racial makeup of the city was 59.71% White, 36.06% Black, 0.29% American Indian, 1.54% Asian, 0.11% Pacific Islander, 1.01% from other races, and 1.30% from two or more races. 2.11% of the population were Hispanic or Latino of any race.

The 2006 revised estimated population was 168,293 which is an 8.4% percent increase over the original 2006 estimate. In 2009, the US Census Bureau estimated that Chattanooga's overall population grew some 9.3% from 2000 to 2008, which is as fast as Tennessee's largest cities. Also, the Census Bureau reported that it estimated that the city of Chattanooga added some 15,326 residents since the 2000 census, for an estimated 2008 population of 170,880 people.

There were 65,499 households out of which 25.3% had children under the age of 18 living with them, 39.2% were married couples living together, 17.3% had a female householder with no husband present, and 39.5% were non-families. 33.5% of all households were made up of individuals and 11.6% had someone living alone who was 65 years of age or older. The average household size was 2.29 and the average family size was 2.92. Same-sex couple households comprised 0.4% of all households.

In the city the population was spread out with 22.4% under the age of 18, 10.8% from 18 to 24, 28.8% from 25 to 44, 22.8% from 45 to 64, and 15.2% who were 65 years of age or older. The median age was 37 years. For every 100 females there were 89.3 males. For every 100 females age 18 and over, there were 85.2 males.

The median income for a household in the city was $32,006, and the median income for a family was $41,318. Males had a median income of $31,375 versus $23,267 for females. The per capita income for the city was $19,689. About 14.0% of families and 17.9% of the population were below the poverty line, including 27.0% of those under age 18 and 13.8% of those age 65 or over.