The partnership will provide Dentsu with access to MSLGroup's network, while providing MSLGroup with a Japanese foothold.
A spokeman for Dentsu explained that the move came as the agency identified the trend of Japanese corporations thinking more globally.
He said: 'More than ever Japanese corporations must turn their sights abroad and build sound relations with stakeholders around the world.
'Dentsu will leverage the network of MSLGroup to further enhance all aspects of client support.'
Through the alliance, Dentsu will have access to over 2,500 employees in 22 countries worldwide.
MSLGroup CEO, Olivier Fleurot added: 'We are uniquely placed to support Dentsu PR and their timely and strategic extension of PR support outside Japan, to their globally-oriented Japanese clients.'
This week the Publicis Groupe also announced the acquisition of affiliates Publicis Romania, Focus Advertising and Publicis Events. The move comes in a bid to strengthen its comms offering in Romania.