As of the census of 2020, there were 67,314 people, 28,912 households, 17,233 families residing in the city. The population density was 1,114.3 inhabitants per square mile (430.2/km2). There were 30,723 housing units at an average density of 500.5 per square mile (193.2/km2). The racial makeup of the city was 72.4% White, 17.3% African American, 0.3% Native American, 2.5% Asian, 0.5% Pacific Islander, 4.6% from two or more races and Hispanic or Latino of any race were 7.1% of the population.
There were 28,607 households of which 29.9% had children under the age of 18 living with them, 40.3% were married couples living together, 14.9% had a female householder with no husband present, 5.1% had a male householder with no wife present, and 39.8% were non-families. 31.6% of all households were made up of individuals and 11.2% had someone living alone who was 65 years of age or older. The average household size was 2.31 and the average family size was 2.95.
The median age in the city was 35.9 years. 23.9% of residents were under the age of 18; 10.4% were between the ages of 18 and 24; 26.4% were from 25 to 44; 25.5% were from 45 to 64; and 14% were 65 years of age or older. The gender makeup of the city was 49.8% male and 50.2% female.
The Waterloo-Cedar Falls Metropolitan Statistical Area consists of Black Hawk, Bremer, and Grundy counties. The area has an estimated population of 167,565. The area had a 2000 census population of 163,706 and a 2008 estimated population of 164,220.
Waterloo is next to Cedar Falls, home to the University of Northern Iowa. Small suburbs include Evansdale, Hudson, Raymond, Elk Run Heights, Gilbertville, and Washburn.