The former boxer and mental health campaigner joined Heineken's Brewing Good Cheer Christmas campaign.
This year 50 pubs across the country will join the campaign, putting on a free festive lunch to help hundreds of lonely people.
"I completely identify with the ethos of Brewing Good Cheer," said Frank. "Pubs are a totally unique British institution, and bring people from all walks of life together unlike anywhere else in the world.
"I think pubs provide a great setting to connect lonely and isolated people and to bring some much needed Christmas cheer."
Frank visited The White Horse in Brixton, close to where he grew up in South London, to see first-hand how the scheme works, joining local charities Opening Doors and Sound Minds.
An estimated nine million people will be alone for a large part of the festivities this year, according to figures from the Red Cross.
- Last year national Poetry Slam champion Solomon O.B worked with the brewer to highlight the campaign.