As well as heading up the UK office, Dundas will head planning for the agency.
Dundas' appointment follows a series of management changes at Nitro. Last week, the agency's planning director Bobby Hui, left without a job to go to.
His departure followed that of the former executive creative director Paul Shearer, and Johan Fourie, the former managing director, who left to set up Arnold UK last year.
Since leaving Saatchis in 2006, Dundas has been assisting his former partner Dave Droga in setting up the agency Droga 5 in New York.
Chris Clarke, the founder of Nitro, said: "Kevin's energy and enthusiasm are infectious and we are delighted to have him lead our gifted UK based team. Kevin will join Kate Howe who continues in her role as managing director, Tom Adams, the head of digital, Chris Nurko, the head of innovation and Richard Russell, the executive creative director. He will also join the Nitro Global Leadership team."