As of the census of 2000, there were 36,287 people, 13,635 households, and 9,367 families residing in the township. The population density was 3,018.3 people per square mile (1,165.6/km). There were 13,932 housing units at an average density of 1,158.8/sq mi (447.5/km). The racial makeup of the township was 62.73% White, 15.27% African American, 0.17% Native American, 14.20% Asian, 0.03% Pacific Islander, 4.70% from other races, and 2.89% from two or more races. Hispanic or Latino of any race were 10.40% of the population.
There were 13,635 households out of which 33.3% had children under the age of 18 living with them, 53.4% were married couples living together, 11.6% had a female householder with no husband present, and 31.3% were non-families. 24.5% of all households were made up of individuals and 7.5% had someone living alone who was 65 years of age or older. The average household size was 2.58 and the average family size was 3.12.
In the township the population was spread out with 23.0% under the age of 18, 8.0% from 18 to 24, 36.5% from 25 to 44, 22.5% from 45 to 64, and 10.0% who were 65 years of age or older. The median age was 35 years. For every 100 females there were 98.7 males. For every 100 females age 18 and over, there were 95.3 males.
The median income for a household in the township is $61,325, and the median income for a family is $70,812 (these figures had risen to $77,658 and $93,931 respectively as of a 2007 estimate). Males have a median income of $48,961 versus $35,971 for females. The per capita income for the township is $28,431. 4.7% of the population and 2.7% of families are below the poverty line. Out of the total people living in poverty, 4.0% are under the age of 18 and 8.5% are 65 or older.
In addition to the township's residents, an average daily population of 1,182 inmates are housed at the Middlesex County Adult Correctional Center, located on Route 130 at Apple Orchard Lane.
Major roads in North Brunswick include:
Amtrak has a freight railyard connected to the Northeast Corridor line at Adams Station, located in the vicinity of Adams Lane and Route 1. New Jersey Transit originates trains to Penn Station in Midtown Manhattan during peak hours from the Jersey Avenue station in New Brunswick. A New Jersey Transit station on the Northeast Corridor Line is being proposed for the former Johnson & Johnson site on Route 1 and Aaron Road by the new owners of the site.