Bellmawr was incorporated as a borough on March 23, 1926, from portions of the now-defunct Centre Township, based on the results of a referendum held on April 21, 1926. The boroughs of Mount Ephraim, Runnemede and Lawnside were also created in the same two-day period.
Bellmawr is home to the main post office for the area, one of the largest in the state of New Jersey. In late October 2001 the office was closed due to possible anthrax contamination (see 2001 anthrax attacks). The office was re-opened several days later, in early November, after testing negative for anthrax.