Merchantville was incorporated as a borough by an Act of the New Jersey Legislature on March 3, 1874, from portions of Delaware Township (now Cherry Hill Township) and Stockton Township.
As of the census of 2000, there were 3,801 people, 1,524 households, and 946 families residing in the borough. The population density was 6,317.2 people per square mile (2,446.0/km²). There were 1,607 housing units at an average density of 2,670.8/sq mi (1,034.1/km²). The racial makeup of the borough was 85.90% White, 7.42% African American, 0.29% Native American, 2.10% Asian, 2.84% from other races, and 1.45% from two or more races. Hispanic or Latino of any race were 5.47% of the population.
There were 1,524 households out of which 32.1% had children under the age of 18 living with them, 45.1% were married couples living together, 12.9% had a female householder with no husband present, and 37.9% were non-families. 32.0% of all households were made up of individuals and 11.6% had someone living alone who was 65 years of age or older. The average household size was 2.48 and the average family size was 3.19.
In the borough the population was spread out with 25.7% under the age of 18, 6.8% from 18 to 24, 31.5% from 25 to 44, 22.1% from 45 to 64, and 13.8% who were 65 years of age or older. The median age was 37 years. For every 100 females there were 89.1 males. For every 100 females age 18 and over, there were 84.6 males.
The median income for a household in the borough was $49,392, and the median income for a family was $60,652. Males had a median income of $43,375 versus $30,771 for females. The per capita income for the borough was $25,589. About 5.8% of families and 6.8% of the population were below the poverty line, including 9.4% of those under age 18 and 3.0% of those age 65 or over.
New Jersey Transit offers bus service to Philadelphia on the 404, 405 and 407 routes.