The Deja Vu star has been dating soul singer Robin Thicke since they were both teenagers and she has only recently told him why they missed out on prom night.
She explains, "I didn't want people to know (we were dating). I didn't want people to call me a sellout or an Oreo, because I'd gotten that my whole life and it wasn't the truth.
"I actually just admitted this to Robin not too long ago."
But Thicke tells Giant magazine he was far from surprised: "She had actually told a couple of people I was black.
"Then prom night comes, we'd been together a year and a half, and she just lies and says she didn't want to go instead of saying she didn't want to take me."
Patton finally gave up her fears about what friends would think about her interracial romance and went public with her boyfriend, who became her husband in 2005.
The couple is now expecting its first child.