The Bee Gees star, who announced earlier this month that he is almost free of the disease, joined military act The Soldiers on stage at the London Palladium last night (February 13) for a charity gig.
The 62-year-old performed classic track 'How Deep Is Your Love' and 'I've Gotta Get A Message To You', his collaboration with the trio of servicemen, at the Coming Home concert in aid of wounded British soldiers.
"Robin looks wonderful, as well as he has done for ages, and his voice was sounding great," an audience member commented to The Mirror.
"He's still got such a unique sound, it was a real honour to watch him as I know he has been very ill. Everyone was thrilled to see him looking so well."
Gibb was given the all-clear to perform at the Palladium back in January while he was still undergoing chemotherapy.
A source said at the time: "He is passionate about the charity and wants to do his bit. Our soldiers are modern-day heroes but as far as they are concerned, Robin's efforts against the odds are every bit as heroic. It'll be an incredibly emotional evening."
He was first rushed to hospital for treatment last November and was also seen by doctors for severe abdominal pains in April 2011.
Listen to Robin Gibb and The Soldiers perform 'I've Gotta Get A Message To You' below: