Lambertville is a city in Hunterdon County, New Jersey, United States. As of the 2010 United States Census, the city's population was 3,906, reflecting an increase of 38 (+1.0%) from the 3,868 counted in the 2000 Census, which had in turn declined by 59 (-1.5%) from the 3,927 counted in the 1990 Census.