According to the United States Census Bureau, the CDP has a total area of 1.2 square miles (3.0 km²), all of it land.
As of the census of 2000, there were 286 people, 120 households, and 75 families residing in the CDP. The population density was 245.5 people per square mile (95.2/km²). There were 148 housing units at an average density of 127.0/sq mi (49.3/km²). The racial makeup of the CDP was 86.01% White, 4.90% Native American, 0.70% Pacific Islander, 4.90% from other races, and 3.50% from two or more races. Hispanic or Latino of any race were 9.79% of the population.
There were 121 households out of which 23.3% had children under the age of 18 living with them, 39.2% were married couples living together, 18.3% had a female householder with no husband present, and 36.7% were non-families. 30.8% of all households were made up of individuals and 15.0% had someone living alone who was 65 years of age or older. The average household size was 2.38 and the average family size was 2.91.
In the CDP the population was spread out with 22.0% under the age of 18, 8.0% from 18 to 24, 22.7% from 25 to 44, 24.1% from 45 to 64, and 23.1% who were 65 years of age or older. The median age was 42 years. For every 100 females there were 83.3 males. For every 100 females age 18 and over, there were 79.8 males.
The median income for a household in the CDP was $26,094, and the median income for a family was $30,500. Males had a median income of $28,750 versus $16,667 for females. The per capita income for the CDP was $14,907. About 19.8% of families and 21.3% of the population were below the poverty line, including 30.3% of those under the age of eighteen and 13.0% of those sixty five or over.
In the state legislature Hornbrook is located in the 4th Senate District, represented by Republican Sam Aanestad, and in the 2nd Assembly District, represented by Republican Doug LaMalfa. Federally, Hornbrook is located in California's 2nd congressional district, which has a Cook PVI of R +13 and is represented by Republican Wally Herger.