Alanna Masterson was born on Long Island to Carol Masterson, a manager, and Joe Reaiche, a Lebanese-Australian former rugby player. Her family later relocated to Los Angeles, California.
Her passion for acting came from spending a lot of time on set with her brothers, both who starred in popular television shows, and from seeing the filming process.
On November 5, 2015, she gave birth to her daughter Marlowe.
- The Young and the Restless
- Definitely Maybe
- Malcolm in the Middle
- Terminator: The Sarah Connor Chronicles
- Grey's Anatomy
- First Day
- Park It Up
- Men at Work
- She is the younger sister of Danny Masterson (Steven Hyde on That '70s Show), Jordan Masterson, Christopher Masterson (Francis on Malcolm in the Middle), and Will Masterson.
- She and her family are Scientologists.
- She built a primary school in Nepal.
- Her half-brother, Christopher Masterson, who starred as Francis on Malcolm in the Middle, helped Alanna score a small role on Malcolm in the Middle.
- She and Chandler Riggs share the same birthday.