Mr. Bernbach, 50, who never achieved the stature of his late father, was traveling and couldn't be reached for comment.
But in a release prepared by DDB Needham holding company Omnicom Group, Mr. Bernbach said: "There are some specific intriguing business and professional opportunities that have come to me, and I felt that now is the moment to pursue them. After 22 years with this company, it is a terribly difficult decision to leave, but I believe it is necessary to do so in order for me to explore these serious options in the greater depth they deserve."
It was speculated Creative Partner Jack Mariucci will also leave soon. Mr. Mariucci and fellow Creative Partner Bob Mackall had worked with Mr. Bernbach on the Seagram Co. account.
Seagram yanked its $37 million in worldwide billings from DDB Needham in early June and put the account in review. Seagram attributed the move to dissatisfaction with the agency.
But the 32-year-old account had a very personal relationship with the agency's founder and then his son, a close friend of Chairman-CEO Edgar Bronfman Jr.
After Mr. Bernbach's demotion to vice chairman, the agency lost Martell cognac, a shift many considered a warning to agency brass.
In the months since, it has been rumored that Mr. Bernbach would leave to join Mr. Bronfman in a business venture or work for one of Seagram's other agencies such as Ogilvy & Mather or Wells Rich Greene BDDP.
But Seagram agency executives said that is an expensive proposition, given Mr. Bernbach's estimated $700,000 a year in annual compensation, half of which it's believed will continue unless he violates a no-compete contract.
Mr. Bernbach, who has 12,050 shares of Omnicom stock, will remain on the board.
But in the Omnicom release, DDB Needham Chairman-CEO Keith Reinhard said: "As president and then as vice chairman, John did an extraordinary job in helping to build the international operations of our agency to its present position of leadership in the world. All of us at DDB Needham wish him the very best in whatever new direction he takes."