The pop star recruited the Big actor for a cameo role in the promo for her new single I Really Like You, and Hanks turned out to film scenes for the project in the Big Apple last month (Feb15).
Jepsen has now revealed the actor stood outside in the bitter wintry weather for hours while he shot his scenes, and she was astounded by his dedication.
She tells U.S. news show Access Hollywood, "The entire day he just wowed me. I don't think he knows he's Tom Hanks. He's just the sweetest, kindest, most humble man you've ever met.
"He was out in the freezing cold, singing my song take after take, while I was in my trailer with my hot chocolate being like, 'Good job Tom! Do it again one more time!'"
Hanks adds of the shoot, "It was stellar. Carly's a cool kid. We had a lot of fun."
Pop star Justin Bieber also features in the video.