As of the census of 2000, there were 161,029 people, 56,488 households, and 39,259 families residing in the city. The population density was 1,531.7/km² (3,967.2/mi²). There were 59,581 housing units at an average density of 566.7/km² (1,467.9/mi²). The racial makeup of the city was 53.6% White, 30.2% Hispanic, 6.3% African American, 5.5% Asian, 1.2% Pacific Islander, 0.4% Native American or Alaskan Native, 0.1% from another race alone, and 3.2% from two or more races. (These figures have been adjusted to classify Hispanics as a separate group from whites, blacks, Asians, and other races; U.S. census data do not separate out Latinos in this manner.)
The area around Oceanside High School was, along with the neighborhood around San Diego High School, the site of the first Samoan communities on the U.S. mainland.
In 2000, there were 56,488 households out of which 35.0% had children under the age of 18 living with them, 54.1% were married couples living together, 11.0% had a female householder with no husband present, and 30.5% were non-families. 22.7% of all households were made up of individuals and 10.2% had someone living alone who was 65 years of age or older. The average household size was 2.83 and the average family size was 3.33.
The age distribution of Oceanside in 2000 was as follows: 27.6% under the age of 18, 10.2% from 18 to 24, 31.0% from 25 to 44, 17.6% from 45 to 64, and 13.6% who were 65 years of age or older. The median age was 33 years. For every 100 females there were 98.0 males. For every 100 females age 18 and over, there were 96.1 males.
The median income for a household in the city was $46,301, and the median income for a family was $52,232. Males had a median income of $34,772 versus $27,962 for females. The per capita income for the city was $20,329. About 8.2% of families and 11.6% of the population were below the poverty line, including 16.2% of those under age 18 and 5.7% of those age 65 or over.
According to estimates by the San Diego Association of Governments, the median household income of Oceanside in 2005 was $61,792 (not adjusted for inflation). When adjusted for inflation (1999 dollars; comparable to census data above), the median household income was $50,177. On June 13, 2005, the Wall Street Journal rated Oceanside as the top vacation home market in the country.