The 44-year-old star and Chmerkovskiy, 34, who was recently seen as a judge on an Indian dance reality show, spent some time with the singer after a concert of Lopez on June 21, reported E! News.
"They partied and seemed really at ease together," a source said.
Lopez and Chmerkovskiy were spotted in the VIP area of the club, along with her entourage and one of his friends.
The group apparently celebrated one of the singer's crew members' birthday.
Chmerkovskiy and Lopez met in November 2013, when they performed together at the American Music Awards.