The Scottish champions made it seven domestic trophies in a row under Brendan Rodgers on Sunday as they defeated Aberdeen 1-0 thanks to Ryan Christie’s first-half strike.
Celtic players were jubilant in their celebrations, joining in with the fans to commemorate the latest success.
Boyhood Celtic fan Tierney took on the role as cheerleader, taking a loudspeaker from the support before leading the players and fans in unison.
The 22-year-old shared a video on Instagram of him shouting into the loudspeaker and gesturing to his team-mates to crouch down before bouncing up and down along with the fans.
Tierney captioned it: “ULTRAS”.
The post was liked by Celtic captain Scott Brown and Scotland colleague Andy Robertson, while Mikael Lustig commented “since he was a boy” in reference to the song the Celtic support sing about Tierney.