In 2009, Union began dating NBA player Dwyane Wade. Union and Wade became engaged in December 2013. Union revealed during a February 2014 interview with Arsenio Hall that she had Wade sign a prenuptial agreement and referred to her previous marriage to Chris Howard. "For this marriage, the biggest difference between this and the last marriage will be a prenup, at my insistence," Union stated. "When you have your own stuff, you don't need to worry about anybody else's stuff... The reality is, I've never seen Dwyane balance a check book, so I got to protect my stuff." In May 2014, the couple announced they would be wed on August 30 in Miami, California on invitations sent out to guests, with an image of Wade's children asking if "Nickie" would marry them. Nickie is Union's nickname, derived from Union's middle name, Monique. Union stated in June 2014 that she coped with Wade's losses by going to work. In July 2014, they announced that guests would not be allowed to bring cell phones or cameras to their wedding.
In May 2010, Dwyane Wade's estranged wife filed a lawsuit claiming Union's relationship with Dwyane Wade was causing her and the Wade's two children "emotional distress." The lawsuit alleged that Union "engaged in sexual foreplay" in front of Wade's children and that Union received "the biggest gift of all" from Wade over his two children during Christmas 2009. Union issued a statement insisting the allegations were false and her attorney C. Anthony Mulrain stated "Each and every allegation made is entirely false". At the time of the filing of the lawsuit, Mulrain said the accusations were first made "about a month ago" in court and Union was not named as a defendant at that time, Mulrain also stating Union apologized "to the Circuit Court of Cook County, Illinois for tying them up with erroneous claims when there are real victims who should be receiving the legal attention they need."
Wade admitted to fathering a son named Xavier Zechariah Wade (b. 2013) with longtime acquaintance Aja Metoyer during a temporary split from Union. In an interview with Glamour magazine, Union blamed her career for the split with Wade. The two have since reconciled their relationship. She explained that she had previously "wanted an awesome career with back-to-back projects, but I realized I wasn't willing to sacrifice my relationship for it." It was reported by New York Daily News that Union's career caused her and Wade to split in 2013. Union stated that her breakup was because of scheduling, as in 2013, she finished filming the first season of Being Mary Jane and then flew to Las Vegas, Nevada right away to start shooting Think Like a Man Too. "I couldn't take time off, and I missed some quality togetherness we desperately needed."
The couple married in Miami,Florida Saturday, August 30 2014 E! News confirms. They were surrounded by family and friends, including the athlete's elder two sons and nephew. The bride wore a stapless Dennis Basso ballgown with a sweetheart neckline as she walked down the aisle.