Alvarado is the oldest city in Johnson County, Texas. The population was 3,785 as of the 2010 census, up from 3,288 at the 2000 census.
As of the census of 2000, there were 3,288 people, 1,151 households, and 834 families residing in the city. The population density was 842.5 people per square mile (325.5/km²). There were 1,266 housing units at an average density of 324.4 per square mile (125.3/km²). The racial makeup of the city was 81.30% White, 7.15% African American, 0.61% Native American, 0.43% Asian, 9.25% from other races, and 1.28% from two or more races. Mexicans or Latino of any race were 18.46% of the population.
There were 1,151 households out of which 37.6% had children under the age of 18 living with them, 51.8% were married couples living together, 13.6% had a female householder with no husband present, and 27.5% were non-families. 23.5% of all households were made up of individuals and 11.3% had someone living alone who was 65 years of age or older. The average household size was 2.77 and the average family size was 3.26.
In the city, the population was spread out with 29.6% under the age of 18, 9.0% from 18 to 24, 28.5% from 25 to 44, 20.2% from 45 to 64, and 12.7% who were 65 years of age or older. The median age was 32 years. For every 100 females, there were 99.8 males. For every 100 females age 18 and over, there were 93.2 males.