The pair appeared to be very close at an Entertainment Industry Foundation gala after the Screen Actors Guild Awards last weekend.
And they reportedly went to another party and were "inseparable," according to sources.
However, an insider is adamant that the relationship between the megastars is simply platonic.
"They're friends," Stuff.co.nz quoted the source as saying to People magazine.
Timberlake, who recently starred in the acclaimed film 'The Social Network', is currently dating actress Jessica Biel.
They are rarely seen at awards ceremonies together, yet the insider maintains the pair is on the right track.
"Justin and Jessica are definitely together. They're happy in their relationship," the source added. (ANI)