Last year it was reported that Williams, 30, has entered a recording studio in her attempt to pursue music career, reported Aceshowbiz.
The rap song goes: "I ball hard no tennis racket/I can't see these haters through my Gucci glasses/I make hits like batting practice -- they be like 'Serena, is you really rapping?'
"That's me, thanks for listenin'/schooling all these rappers, they should pay tuition/ I make a lot of money but that ain't yo business/you can tell the people I said this."
She also makes a reference to her sister Venus Williams, rapping, "I win, I really mean it/Swag out this world, you should call me Venus/That's my sister, my name is Serena/on the court I serve 'em up, no subpoena."
Williams had a recording session at B Major Music Group, a studio owned by her good friend, Baltimore Ravens player Vryant McKinnie.