Decker's Chapel is a historic chapel on Earth Road and PA 255 in St. Marys, Elk County, Pennsylvania within the Diocese of Erie.

It was built in 1856 and is a one-story gable-end oriented and clapboard clad wood-frame structure.

It features a rectangular steeple with an open belfry capped with a cross tipped, pyramidal roof.

Also on the property is a granite commemorative marker dedicated in 1928 to Monsignor Michael Joseph Decker.

[2] It was added to the National Register of Historic Places in 1998.