The Canadian singer performed the acoustic versions of "Love yourself" and "Cold water" to pay tribute to the victims of the terror attack at Ariana Grande's May 22 gig in the British city that claimed 22 lives, reported Us weekly.
"I'm not going to let go of hope. I'm not going to let go of love. I'm not going to let go of God... Put your hand up if you're not going to let go," Bieber, 23, told the crowd at the Old Trafford Stadium.
Besides Bieber, the three hour-long concert, organised and headlined by Grande, also saw artistes such as Coldplay, Take That, Robbie Williams, Pharrell, Miley Cyrus, Niall Horan, The Black Eyed Peas, Imogen Heap, Katy Perry performing on their hits.
Grande also got emotional while recalling her meeting with the mother of 15-year-old victim, Olivia Campbell, who died in the terrorist attack at her concert last month.