Martins Creek is a census-designated place in Lower Mount Bethel Township, Pennsylvania located along Martins Creek. Its population was 664 as of the 2020 U.S. census. Martins Creek is part of the Lehigh Valley metropolitan area, which had a population of 861,899 and was the 68th-most populous metropolitan area in the U.S. as of the 2020 census. The Zip Code is 18063.