Watch: The Wanted backstage at Tom Parker's Inside My Head concert
The 33-year-old father-of-two, who was diagnosed with incurable brain cancer last summer, joined bandmates Max George, Jay McGuiness, Nathan Sykes and Siva Kaneswaran for the Inside My Head show to raise money for Stand Up To Cancer and the National Brain Appeal.
Parker shared a video of fans outside the concert hall in London chanting "We love Tom!".
He said: "Wow, what a night, thank you all from the bottom of my heart sorry I couldn’t come out and see you all. Covid Covid but thank you all for the support. It means so much xx."
The band shared a group hug on stage when Parker started to tear up during the show, and were supported by their cheering fans.
Parker shared a picture of the moment saying: "Managed to get a bit of sleep. Still on a high from the concert."
A message on the band's Instagram account said: "A night we'll never forget. So proud of our bro @tomparkerofficial Huge THANK YOU to everyone who came down to the @royalalberthall for Tom's 'Inside My Head' concert. It was such an incredible night for us all and great to see so much support for @su2cuk. Thanks to all the amazing performers too. #StandUpToCancer #InsideMyHead."
They also shared a throwback snap of the last time they all performed together before they split in 2014, captioned: "The last time we performed together was sooo long ago, look how young we look!!"
The Wanted formed in 2009 and dominated the charts after the release of their single All Time Low in 2010, which went straight to number one.
In the space of just three years, they clocked up nine more top 10 singles – going again to number one with Glad You Came in 2011.
Since they split, Sykes and Kaneswaran, 32, have pursued solo music careers, George has tried his hand at acting, McGuinness, 30, was the winner of Strictly Come Dancing in 2015 and Parker competed in Channel 4 skiing show The Jump in 2016.
Parker announced last year that he had been diagnosed with an inoperable stage four brain tumour, but vowed he would fight the condition. He is now married to Kelsey, with whom he shares two young children.
Read more: Tom Parker making brain cancer documentary
George confessed earlier this year that he battled depression and underwent brain scans in the wake of the band's split in 2014 – and spent three weeks essentially confined to his apartment.