The senator and his wife Cindy took part in the 75-minute service at the North Phoenix Baptist Church and shook hands with greeters, ushers and church members before and after the ceremony.
McCain had remained out of sight for most of the holiday weekend and many of the hundreds of worshippers did not seem to notice that he was sitting in the church with his wife.
The theme of the sermon by Pastor Dan Yeary was that people can lift their spiritual lives through sacrifice.
Shortly after the church service, McCain and his wife went to a Veterans Affairs hospital in central Phoenix for a 45-minutes visit.
McCain, who was flanked by Secret Service agents, did not speak to reporters at the church or at the hospital.
He plans to fly to Denver on Monday for a town hall meeting.
