Jenison is a census-designated place in Ottawa County in the U.S. state of Michigan. The community is located within Georgetown Charter Township. The population of the CDP was 17,211 as of the 2000 census. The current estimated population for the entire Jenison ZIP code, 49428, is 25,770. The geographical boundaries of the ZIP code are larger than that of the CDP. It is a bedroom community in proximity to Grand Rapids.