While attending a revival meeting in 1907, McPherson met Robert James Semple, a Pentecostal missionary from Ireland. She dedicated her life to Jesus and converted to Pentecostalism. At the meeting, she became enraptured by Semple and his message. After a short courtship, they were married in an August 1908 Salvation Army ceremony. Semple supported them as a foundry worker and preached at the local Pentecostal mission. They studied the Bible together, then moved to Chicago and joined William Durham's Full Gospel Assembly. Durham instructed her in the practice of interpretation of tongues.