The duo spoke through webcam on Tuesday and discussed first connecting with each other at the 2002 MTV VMA Awards.
Fallon was hosting the event while Timberlake was set to perform as a solo artist for the first time.
"I was like pacing and I'm like, 'I'm so nervous. I hope this hosting thing goes well because you know if I host this and that's my career.' And you go, 'Yeah, well, this is my first solo thing ever,'" Fallon said about the conversation that they had backstage.
Timberlake ended up performing his single "Like I Love You" for the first time.
"In retrospect, maybe not the greatest decision. Maybe I should have put the song out first so people knew who I was," the singer said.
Timberlake said that when their friendship first started, the pair didn't take everything too seriously.
"We kind of like, we started doing bits back and fourth, you know, and that's all we do now," Timberlake said.
Timberlake stars in the animated sequel Trolls World Tour which will be released digitally Friday as the COVID-19 pandemic has closed down movie theaters.