2020 census

As of the 2020 census, Bethany had a population of 31,350. The median age was 36.9 years. 30.0% of residents were under the age of 18 and 10.3% of residents were 65 years of age or older. For every 100 females there were 94.7 males, and for every 100 females age 18 and over there were 92.0 males age 18 and over. ^{[6] [7]}

99.9% of residents lived in urban areas, while 0.1% lived in rural areas. ^[8]

There were 10,719 households in Bethany, of which 50.3% had children under the age of 18 living in them. Of all households, 67.7% were married-couple households, 10.0% were households with a male householder and no spouse or partner present, and 18.5% were households with a female householder and no spouse or partner present. About 17.2% of all households were made up of individuals and 7.1% had someone living alone who was 65 years of age or older. ^[6]

There were 11,159 housing units, of which 3.9% were vacant. The homeowner vacancy rate was 1.5% and the rental vacancy rate was 4.8%. ^[6]

2010 Census

As of the census ^[9] of 2010, there were 20,646 people, 7,205 households, and 5,579 families residing in Bethany. The racial makeup of Bethany was 60.4% White, 31.7% Asian, 1.7% Black, 0.2% Pacific Islander, 1.5% from other races, and 4.1% from two or more races. Hispanic or Latino of any race were 5.1% of the population.

There were 5,579 family households, of which 50.6% had children under the age of 18 living with them, 66.4% were married couples living together, 8.4% had a female householder with no husband present, 2.6% had a male householder with no wife present, and 22.6% were non-families. 18.6% of all households were made up of individuals, and 6.6% had someone living alone who was 65 years of age or older. The average household size was 2.86 and the average family size was 3.30.

The median age in Bethany was 35.7 years. The gender makeup of the area was 48.5% male and 51.5% female.