The Take That frontman is said to have teamed up with the pop icon for his upcoming third solo album, according to The Mirror.
The pair are reported to have joined up with each other in a New York studio last month.
Barlow announced plans for his first full solo album in 14 years last week, to be released on November 25.
The LP will be released the week after bandmate Robbie Williams's latest album Swings Both Ways.
Gary Barlow recently said of Elton John at the singer's BRITs Icon ceremony: "I started to play the piano because of one person, Elton John.
"When your music is that good and you're that talented, the world is going to love you."
Elton John reached number three with his 31st album The Diving Board at the weekend.