Developed as a multi-use recreational facility to compliment Macombs Dam Park to the south, the park is named for John Mullaly, a founder of the New York Park Association. The first playground opened on the site in 1932, and in 1942, handball, basketball, paddle tennis, volleyball, ice skating, and roller skating facilities were introduced at its southern end. In the late 1960s, the addition of a swimming pool, bathhouse, ice rink, and snack bar were financed by the Land and Water Conservation Fund. Softball fields and tennis courts were added in the early 1970s. Two playgrounds, two small soccer fields, a new irrigation system, new benches, and a granite compass rosette were introduced in 2001. In 2008 improvements were made to the park with mitigation funds from the construction of the Croton Water Filtration Plant and as part of the mitigation plan undertaken when the new Yankee Stadium took over Macombs Dam Park and part of the then 18.5-acre Mullaly Park.
Bisected by East 165th Street and bordered by Jerome Avenue, McClellan Street, River Avenue, and East 164th Street, the roughly rectangular park is organized around a central circular play fountain featuring dolphin fountainheads. Paths radiate from the fountain to each corner of the park and along the horizontal and vertical axes. The fountain is flanked on two sides by large rectangular planting beds (which are subdivided into three concentric rectangular hedgerows) and on the other two by playfields. On the north end of the park, two playgrounds are surrounded by mature trees. The southern section of the park features one of the city’s first skate parks, installed in 1988, as well as a pool, basketball courts, and an additional playground.