The actress has joined with Olympic partner Panasonic to launch its new Flag Tags Facebook app, which allows people to virtually draw their nation's flag onto their face.
"I'm delighted to be a part of the Panasonic Flag Tags campaign to get people supporting Team GB," Tointon said.
"I'm really excited about the Games coming to London and am so proud that we've been chosen to host such a prestigious event."
She added: "Face painting is a great way of showing your patriotism and I had such a laugh playing around with painting the Union Jack on my face.
"With my boyfriend Artem [Chigvintsev] being Russian, I may need to make one half of my face a Union Jack and the other half a Russian flag!"
Gaele Lalahy, digital communications manager of Panasonic UK, says: "Kara is such a big fan of the Olympic Games and we are thrilled to have her on board with the Flag Tags campaign.
"She looks beautiful in the pictures and we hope people will join her in showing their support for Team GB."
"Our specially created Flag Tags app is a simple way of helping people show support for their favourite team by painting their nation's flag on their face and sharing it with their friends."