The singer-songwriter was one of three celebrities to have their identities revealed during Saturday’s final of the ITV competition.
After being revealed as the winner, Joss, who was pregnant at the time of filming, said: “Life can be too serious, we should just dress up in chips and sausage and have a sing song.”
She added: “This has been the funnest, most hilarious job I have ever had. I have laughed so much.”
The judges failed to guess her identity.
Joss, whose hits include You Had Me and Walk With Me, saw off competition from fellow singers Ne-Yo and Aston Merrygold.
JLS star Aston became the first famous face to have their identity revealed after Robin was unmasked.
The former boybander said appearing on The Masked Singer was a “brilliant” experience.
When asked if his fellow JLS band members knew he was on the show, he added: “No. Hi guys.”
US singer Ne-Yo made it into the final as Badger.
“I’ve had so much fun with this, I really have,” he told viewers after being unmasked.
“It’s a great experience, man. I would happily do it again but I might have to work a little harder to fool you guys.”
Girls Aloud star Nicola Roberts, who won the first series as Queen Bee, made a return to the programme as a guest judge.
She was adamant Badger was Ne-Yo before he took his mask off, and said she instantly recognised his voice.
The Masked Singer sees famous contestants don elaborate costumes as they sing in front of a celebrity panel who are tasked with trying to guess their identity.
Singers Sophie Ellis-Bextor, Mel B, Morten Harket and Gabriele, comedian Sir Lenny Henry, television presenter Sue Perkins, actor John Thompson, former footballer Glenn Hoddle and actress Martine McCutcheon had their identities revealed earlier on the series.