The tennis star hit Baltimore Ravens lineman Bryant McKinnie's studio in Florida to record some songs last year and TMZ.com revealed a minute-long sample Friday.
Judging by the untitled track, the 30-year-old former No. 1 player is a lot better than a lot of other athletes turned wanna-be rappers.
"Baby, Serena, is you really rapping? That's me, thanks for listening," Williams raps on the track. "Schooling these rappers, they should pay tuition.
"I put the track up like a frozen pizza. Beats so crazy it might blow your speakers."
If the rap thing doesn't work out, Williams still has a pretty good career in tennis to fall back on. She crushed No. 2 seed Maria Sharapova, 6-1, 6-3, Friday to advance to the Madrid Open semi-finals.