Mia is also the half-sister of actress Liv Tyler. She has appeared in several films herself, including a cameo role in O Brother, Where Art Thou?, and Rush Hour 3. She has appeared on MTV as a VJ for House of Style and was featured in the reality show Celebrity Fit Club in 2005. She lost 18 pounds during production of the show but Tyler has always believed that beauty comes from within. In 2009, Mia appeared as a judge on the Oxygen show Pretty Wicked.
Tyler spent most of her childhood growing up on Lake Sunapee. Her parents divorced in 1987 and she continued living with her mother for several more years in New Hampshire before moving to New York in 1990, when Mia was 12. Her mother developed a brain tumor and was given 18 months to live in 1997. Mia remained by her side, choosing to forgive the past despite a difficult relationship with her mother, until Cyrinda's death in 2002.
In 2003, Mia married the former drummer of the rock band Papa Roach, Dave Buckner, on stage at an Aerosmith show. They divorced in 2005. She was engaged to drummer Brian Harrah, but they split in August 2008.
Mia has always been vocal about helping others with weight issues. She continues to be a role-model to plus-size young women through her My Space page and interviews that she has done on shows like the Tyra Banks Show. In 2007, she decided to write a memoir about her struggles with her weight, her oft-contentious relationship with her mother and her battles with addiction and self-mutilation. Her book, "Creating Myself: How I Learned That Beauty Comes in All Shapes, Sizes, and Packages, Including Me" chronicles the good, the bad, and even the ugly sides of her life. The book was released on August 26, 2008.