In June of 1829, Christian Whitmer, along with several of his brothers became one of the Eight Witnesses of the Book of Mormon. He and Ann were baptized into the newly organized church on April 11, 1830. Christian was called on missions, served in several church positions, and accompanied his family and the church to Ohio and Missouri. In Jackson County, Christian was appointed a leading elder of the church.
By 1835, Whitmer and his family had relocated to Far West, Missouri, where Whitmer sat on the High Council. He had health problems and died on November 27, 1835, leaving no children. His widow Ann eventually returned to Fayette, New York.