The Scottish singer-songwriter donned the mask for his set on the main stage of TRNSMT in front of around 50,000 people in Glasgow Green.
His appearance as the Star Wars character came amid a spat with Noel Gallagher who called him "Chewbacca" as well as saying he should "enjoy his 15 minutes" and calling Scotland a "third world country".
The mask is now being auctioned by DF Concerts on eBay for the charity Tiny Changes - which was set up in May in memory of Frightened Rabbit frontman Scott Hutchison, who took his own life last year.
It is owned by the company's concert manager, who said: "I had a feeling after all the Noel Gallagher back and forth with Lewis Capaldi, that they may be in need of a Chewbacca mask so I got in touch with Lewis's team and offered my mask. The answer was 'bring it!'.
"I've worked with Lewis since he was doing small club shows so to see him play in front of a sold out crowd at TRNSMT was a special moment, made all the more special by seeing my mask out there.
"The whole team at DF were devastated by the loss of Scott Hutchison last year and Frightened Rabbit are another band that we've shared some special moments with.
"So I thought I'd see how much we could raise for Tiny Changes, the charity set up by his family in his memory.
"Its main focus is to raise awareness about young people's mental health issues. Hopefully there will be a bidding war and lots of money will be raised."
Music fans have until around 1.30pm on Monday to bid for the mask.
The band said in a tweet: "The bold @LewisCapaldi has signed the Chewbacca mask he wore for @TRNSMTfest and it is being auctioned off with proceeds going to @tinychanges.
"Who agrees @NoelGallagher should chip in with a bid?"