Rolling Stone magazine said Perry was in the audience for the opening night of Mayer's "Born and Raised World Tour" during which he said he was singing the ballad for "Katy, who is my face to call home."
Mayer also publicly thanked Perry for helping him deal with vocal chord problems that left him unable to sing for about 20 months.
"She was so patient," he told the audience.
Mayer said despite his health issues Perry took the time "to continue to get to know me and love me."
The couple began dating last August but have broken up several times, most recently in March, People.com said. They recently reconciled.