He had already performed "Don't Look Back in Anger", the 1996 Oasis hit that has become an anthem in Manchester since the suicide bombing.
When one fan joked about the dimming prospect of the two reuniting in light of Gallagher's tweets, the singer responded by drawing the attention away from Oasis and back to his brother's behavior.
"What an incredible night last night pure love vibrations nobody comes close to Manchester love forever", Liam, 44, wrote, before adding.
The musical night was organised by Ariana Grande to raise funds to support the families of those killed and injured at the recent terror attack during her concert in Manchester on 22 May.
Liam Gallagher says he "takes back" all of the negative comments he's ever made about Coldplay in the past. "It's about people helping other people and he's once again shown his true f****** colours".
One Love Manchester was live streamed on Facebook, YouTube and over 30 television networks internationally, and featured a star-studded line up that included Coldplay, Justin Bieber, Katy Perry, Take That, Robbie Williams and Miley Cyrus.
A spokesperson for Noel Gallagher said: 'Sadly, Noel will not be at the concert this weekend.
He said working with his brother "bores the death" out of him, adding: "He's changed, as a person".
Noel had already denied he would be showing up because he and his band High Flying Birds were booked to play elsewhere, explaining, "I'm up for it but I think we're booked for a gig somewhere". If he wants to write things down I'll give him a pen and a pad of paper. "He's part of the establishment", he told a crowd.