Okeechobee County was created in 1917. It was named for the Lake Okeechobee, which was itself named for Hitchiti words oka (water) and chobi (big).

As of the census of 2000, there were 35,910 people, 12,593 households, and 9,016 families residing in the county. The population density was 46/mi². There were 15,504 housing units at an average density of 20/mi². The racial makeup of the county was 79.28% White, 7.92% Black or African American, 0.54% Native American, 0.67% Asian, 0.04% Pacific Islander, 9.56% from other races, and 1.99% from two or more races. 18.61% of the population were Hispanic or Latino of any race.

There were 12,593 households out of which 30.40% had children under the age of 18 living with them, 55.50% were married couples living together, 10.70% had a female householder with no husband present, and 28.40% were non-families. 21.50% of all households were made up of individuals and 10.10% had someone living alone who was 65 years of age or older. The average household size was 2.69 and the average family size was 3.07.

In the county the population was spread out with 25.20% under the age of 18, 9.50% from 18 to 24, 27.10% from 25 to 44, 21.90% from 45 to 64, and 16.30% who were 65 years of age or older. The median age was 37 years. For every 100 females there were 115.50 males. For every 100 females age 18 and over, there were 115.20 males.

The median income for a household in the county was $30,456, and the median income for a family was $35,163. Males had a median income of $25,574 versus $20,160 for females. The per capita income for the county was $14,553. About 11.80% of families and 16.00% of the population were below the poverty line, including 19.90% of those under age 18 and 10.30% of those age 65 or over