McLean shared a video of the two dancing on social media, with the caption, "Ran into the bro @liampayne at the secret society of boyband members meeting!! Lol #StripThatDown #Everybody #AJSoloAlbum."
The 39-year-old Backstreet Boy teased the meeting with the 23-year-old earlier that day.
"It's a chillin kinda Tuesday! Gonna be doing something fun today with Liam from one direction so stay tuned ????" he posted.