PK Music Performance executives have filed suit against the hitmakers, accusing them of sampling Perry Kibble's 1969 tune, "A New Day Is Here At Last", on their 2006 "Damn Girl" hit without permission, reported the New York Daily News.
The music bosses own the rights to the funky disco track, written by Kibble, who died in 1999, and recorded by J C Davis.
PK Music officials claim "Damn Girl" features their song's drum beats and guitar riffs, and various organ and saxophone parts.
The executives want a cut of Timberlake and Will.I.Am's profits from their collaboration.