A source told UsWeekly.com, "They are really good friends still and speak all the time, but their schedules just made it too difficult and it fell apart. Maks has a lot of respect for her, but it just wasn't working anymore."
Upton, 21, and Chmerkovskiy, 33, went public with their romance in September.
Maks told “Extra” in October, “Things are going great… I think I got lucky… she's an amazing girl.” He added, “Everyone is happy, we are enjoying each other’s company.”
“Extra” also spoke with Upton around the same time. She gushed then, “We’re having a lot of fun and I have met his family. He has really great people around him. I think that’s part of his appeal.”
Rumors have it Sports Illustrated Swimsuit model Kate Upton and dancer Maksim Chmerkovskiy have split after six months of dating.