Aside from her soccer stardom, Mia Hamm's personal life has thrived. She has been married twice, first to her childhood sweetheart Christiaan Corry, then Boston Red Sox shortstop Nomar Garciaparra. Mia and Nomar share three children: twin daughters Grace Isabella and Ava Caroline in 2007 and a son, Garrett Anthony, in 2012.

Additionally, before she retired from soccer, Mia founded the Mia Hamm Foundation following the death of her adopted brother Garrett from complications of aplastic anemia. Garrett had been suffering for ten years from the rare bone marrow disease before passing away in 1997. Mia's foundation is focused on two goals: supporting bone marrow transplant patients and their families and young women in sports.

The Mia Hamm Foundation now annually hosts "The Mia Hamm and Nomar Garciaparra Celebrity Soccer Challenge," which encourages celebrities to participate in a charity soccer game where the proceeds benefit bone marrow transplant patients and their families. But this isn't the only way that Mia remains in touch with the sport she loves.

In 2014, Mia became the co-owner of Los Angeles FC. The club is a Major League Soccer team, and in 2020, Los Angeles FC was the runners-up in the CONCACAF Champions League. Additionally, Mia joined then-Vice President Joe Biden and Second Lady Dr. Jill Biden at the 2015 FIFA Women's World Cup Final to enjoy the game. In 2021, Mia was inducted into the National Women's Hall of Fame.