According to the Department of Finance for the State of California, Patterson's population in 2014 was 20,922. The 2010 United States Census reported that Patterson had a population of 20,413. The population density was 3,428.5 people per square mile (1,323.7/km²). The racial makeup of Patterson was 10,117 (49.6%) White, 1,291 (6.3%) African American, 221 (1.1%) Native American, 1,069 (5.2%) Asian, 280 (1.4%) Pacific Islander, 6,235 (30.5%) from other races, and 1,200 (5.9%) from two or more races. Hispanic or Latino of any race were 11,971 persons (58.6%).
The population was spread out with 6,890 people (33.8%) under the age of 18, 2,140 people (10.5%) aged 18 to 24, 5,822 people (28.5%) aged 25 to 44, 4,280 people (21.0%) aged 45 to 64, and 1,281 people (6.3%) who were 65 years of age or older. The median age was 29.1 years. For every 100 females there were 101.1 males. For every 100 females age 18 and over, there were 98.0 males.