Post Offices in Mahwah, New Jersey, United States SearchSearch SearchSearch View: Grid 1View: Grid 2View: Grid 3View: Grid 4View: Grid 5View: List Mahwah Post Office No Reviews Favorite Phone: (201) 512-9928Retail Hours Mahwah Carrier Annex Post Office No Reviews Favorite Fax: (650) 577-4090Phone: (201) 760-0892Retail Hours