Gilbertsville is a census-designated place (CDP) in northwest Montgomery County, Pennsylvania, United States. It is located in Douglass Township at the junction of Routes 73 and 100. The population was 4,832 at the 2010 census, and the ZIP code is 19525. The name is also applied to an indeterminate adjacent section of New Hanover Township served by the Gilbertsville Post Office, and in fact the New Hanover Township offices are located in an area considered to be part of Gilbertsville.