Old Tappan ( tə-PAN) is a borough in Bergen County, New Jersey, United States. As of the 2010 United States Census, the borough's population was 5,750, reflecting an increase of 268 (+4.9%) from the 5,482 counted in the 2000 Census, which had in turn increased by 1,228 (+28.9%) from the 4,254 counted in the 1990 Census.
Old Tappan was incorporated as a borough by an act of the New Jersey Legislature on October 18, 1894, from portions of Harrington Township, based on the results of a referendum held two days earlier. The borough was formed during the "Boroughitis" phenomenon then sweeping through Bergen County, in which 26 boroughs were formed in the county in 1894 alone. On April 23, 1896, additional territory was annexed from Harrington Township. The borough's name is derived from the Tappan tribe of Native Americans.
According to the United States Census Bureau, the borough had a total area of 4.16 square miles (10.78 km2), including 3.32 square miles (8.59 km2) of land and 0.85 square miles (2.20 km2) of water (20.38%).
One of only four confluence points in New Jersey, the 41°N 74°W crossing, is in Old Tappan on watershed property owned by United Water.
The borough is bordered to the north by the hamlets of Pearl River and Tappan in the town of Orangetown in Rockland County, New York. Lake Tappan and the Hackensack River are on the western side of the town, bordering River Vale. Harrington Park is to the south and Northvale and Norwood are to the east.
The 2010 United States Census counted 5,750 people, 1,931 households, and 1,593 families in the borough. The population density was 1,725.8 per square mile (666.3/km2). There were 1,995 housing units at an average density of 598.8 per square mile (231.2/km2). The racial makeup was 74.78% (4,300) White, 0.73% (42) Black or African American, 0.09% (5) Native American, 22.24% (1,279) Asian, 0.00% (0) Pacific Islander, 0.63% (36) from other races, and 1.53% (88) from two or more races.