Puttnam, the producer of cinema hits including Chariots of Fire and The Killing Fields, will work closely with TBWA's branded content division, TBWA\Stream, to focus on film- and youth-related projects.
This year, TBWA has developed its non-traditional advertising output and has been involved in advertiser-funded TV programming for Adidas and The Sun, as well as releasing a CD for McCain.
Andrew McGuinness, the chief executive of TBWA, said: "We all know that we need to move beyond traditional advertising channels. TBWA is determined to make it a reality. Lord Puttnam will be central to us continuing to achieve this."
Puttnam moved into film producing from advertising in the early 80s.
He was an account executive at Collett Dickenson Pearce in its glory days in the 60s, when he worked with Charles Saatchi and Ross Cramer.