There were 5,233 households out of which 36.7% had children under the age of 18 living with them, 55.9% were married couples living together, 11.9% had a female householder with no husband present, and 27.4% were non-families. 21.6% 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 2.73 and the average family size was 3.23.
In the CDP the population was spread out with 20.8% under the age of 18, 6.8% from 18 to 24, 42.8% from 25 to 44, 21.0% from 45 to 64, and 8.6% who were 65 years of age or older. The median age was 36 years. For every 100 females there were 134.3 males. For every 100 females age 18 and over, there were 145.2 males.
The median income for a household in the CDP was $54,929, and the median income for a family was $61,029. Males had a median income of $48,000 versus $31,804 for females. The per capita income for the CDP was $19,794. About 6.1% of families and 9.6% of the population were below the poverty line, including 8.1% of those under age 18 and 6.6% of those age 65 or over.
As part of the 2000 Census, 13.65% of Avenel's residents identified themselves as being Indian American. This was the fifth highest percentage of Indian people in any place in the United States with 1,000 or more residents identifiying their ancestry.