The 33-year-old was overlooked for the Scots' upcoming clashes with Argentina, New Zealand and Tonga but said it would be an honour to lead the prestigious invitational outfit.
"It's something so many fantastic players have done before and when John Kirwan asked me to be the skipper that has just added to the privilege," Kellock said.
"The Barbarians is about the old school values of rugby and everything that's good about them as well as a high level of performance, and getting that level of performance right is important."
The Barbarians have been forced into two changes for the matches against the Wallabies and the Leicester Tigers, next Tuesday.
Sharks prop Lourens Adriaanse comes onto the bench after Coonie Oosthuizen's South Africa call-up, while Blues wing Tevita Li replaces Patrick Osborne.
Cheika says Test spots will be up for grabs in the match but victory remains a priority for Australia.
Former Wallabies winger Cummins expects a fierce battle against his ex-teammates and plenty of expansive, attacking rugby.
"Have a run, swing it wide, that's the go I reckon," the former Western Force winger said.
"It's the best for all I think, for the players and the fans. That's what it's all about."
Barbarians: Tim Nanai Williams (Chiefs), Frank Halai (Blues, New Zealand), Juan de Jongh (Stormers, South Africa), Francis Saili (Blues, New Zealand), Nick Cummins (Coca Cola West Red Sparks, Australia), Colin Slade (Crusaders, New Zealand), Tomas Cubelli (Belgrano Ath, Argentina); Steven Luatua (Blues, New Zealand), Matt Todd (Crusaders, New Zealand), Adam Thomson (Canon Eagles, New Zealand), Alastair Kellock (Glasgow, Scotland), Dominic Bird (Canterbury, New Zealand), Angus Taavao (Blues), James Parsons (Blues), Matt Stevens (Sharks, England). Res: Mahonri Schwalger (Chiefs, Samoa), Thomas Du Toit (Sharks), Lourens Adriaanse (Sharks), Heinrich Brussow (Cheetahs, South Africa), Matias Alemanno (La Tablada, Argentina), Sarel Pretorius (Cheetahs), Joaquin Tuculet (Grenoble, Argentina), Marnitz Boshoff (Golden Lions, South Africa).