Shawn Mendes made a surprise appearance on stage at Niall Horan's concert in London.

The Stitches singer joined Horan at the OVO Arena Wembley for the performance of Mendes' hit song, Treat You Better.

Before starting, Horan humorously commented on Mendes' physique, saying, "By the way, I was just thinking, waste of time going to the gym."

Mendes playfully replied, "If you're gonna wear a tank top, I'm gonna wear a tank top."

In the videos shared by fans, Horan said, “Let's do this thing, brother,” and then the duo can be seen playing an acoustic rendition of the Mendes' song, Treat You Better.

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The former One Direction member proudly referred Mendes as, “That’s my boy,” after he left the stage.

This surprise appearance comes after the Señorita singer was spotted attending Paris Fashion Week event in the day.

Notably, this marks Shawn Mendes' second public performance since cancelling his Wonder World tour in 2022 to prioritize his mental health.

Earlier, he made a surprise appearance at Ed Sheeran’s concert, where the duo performed two song, Lego House and There’s Nothin’ Holding Me Back.