The township was named for George Washington, one of more than ten communities statewide named for the first president. It is one of five municipalities in the state of New Jersey with the name "Washington Township". Another municipality, Washington Borough, is completely surrounded by Washington Township, Warren County. Growth in the area exploded after the Civil War with the completion of the New Jersey and New York Railway through the Pascack Valley, as communities were established near the railroad's stations.

Orvil Township was created on January 1, 1886, from the western portion of The Township of Washington and the southern portion of Hohokus Township.

Seven Chimneys is a house with the described seven chimneys, located on Ridgewood Road atop a small hill. George Washington is said to have stayed at the house during the Revolutionary War. Seven Chimneys, the oldest house in the township, is an impressive example of eighteenth-century, regional, domestic architecture and is an important remnant of the community's early settlement period. The house is listed on the State Register and National Register of Historic Places. Notable visitors include Theodore Roosevelt. The house was used as a stop on the Underground Railroad during the Civil War. On November 3, 1968, the Bergen County Historical Society placed a historic-site marker on the property and was placed on the National Register of Historic Places in 1971.

During the mid-1950s, the completion of the 173-mile (278 km) Garden State Parkway split the township in two. The Parkway created two access routes with Exit 166 on the southern border closest to Paramus and Exit 168 on Washington Avenue. The northernmost toll plaza was built off of East Glen. During the decade after the Parkway was completed, the township dramatically increased in population.

ZIP Code 07677 for Township of Washington was established effective July 2000. Previously, the township had been served by the Westwood post office as ZIP Code 07675

Progressive American cuisine, award-winning wine collection, and friendly, professional service create an unforgettable dining experience at Bacari Grill. Special Occasions are the hallmark of their upscale venue. Indulge in menu selections of your choice. They are happy to make wine recommendations, or, view their award-winning collection and select your favorites.