New Cassel is a hamlet and census-designated place (CDP) in the Town of North Hempstead in Nassau County, on Long Island, in New York, United States.

[3][4] After World War II, it became home to a great number of successful middle class families, including many Black and Latino veterans.

[3] By the second half of the 20th century, New Cassel had become home to a growing number of Haitian and Latino families.

[4] When the adjacent village of Westbury incorporated in 1932, New Cassel chose not to be absorbed over fears that taxes would rise.

[5] As such, it would remain an unincorporated hamlet directly governed by the Town of North Hempstead in Manhasset.

[5][6] According to the United States Census Bureau, the CDP has a total area of 1.5 square miles (3.9 km2), all land.