Warren Gatland's first match after stepping down as Wales boss this autumn will be against the team he has guided for over a decade.
The first meeting between the sides since 2012 will also be Wayne Pivac's first outing as successor to Gatland.
"It goes without saying that this match has huge significance to me," said Gatland, who is next week set to be unveiled as Lions boss for the 2021 tour to South Africa.
"Wales has been my home for the last 12 years and I have thoroughly enjoyed my time here.
"We have had some great success with Wales and we are currently in a hugely important year, culminating at the World Cup.
"To have the opportunity to return to Cardiff after the World Cup is fantastic.
"It will be an honour to coach the Barbarians, they symbolise the very best of rugby tradition and are an important part of the international game and I'm hugely looking forward to being part of the Baa-baas club."
Completing the double header on November 30 will be a first meeting between women's teams representing Wales and the Barbarians.
Tickets for the Wales v Barbarians autumn international match are expected to go on general sale in August, priced from £10 to £50.