Kershaw will succeed James Best, the BMP DDB group chairman, who has decided to step down after five years, even though the chairmanship is not for a fixed term.
A long-established figure on the agency scene, Kershaw is seen as having the experience and high-level contacts necessary to help sustain the AA's influence in Whitehall and Brussels.
His appointment maintains the AA's practice of having a senior adman as the chairman and a top advertiser as the president. That office is held by Sir Niall Fitzgerald, the Unilever chairman.
Kershaw takes the chairmanship as the AA faces perpetual battles to keep UK ministers and EU legislators on its side, amid threats to clamp down on advertising to children, and fresh curbs on alcohol promotion.
"David is a grown-up, who has been around long enough to have experienced most of the things that have happened in advertising,
an AA source commented.
Kershaw is a member of the IPA council and was appointed by its president, Bruce Haines, to lead a working party to look at how the trade body should be restructured.
Kershaw is one of the closest associates of Charles and Maurice Saatchi.
He joined Saatchi & Saatchi as an account director in 1984, rising through the ranks to become the managing director and, later, the chairman of the Charlotte Street agency.
He is steeped in the Saatchi culture and has remained fiercely loyal to the brothers. He resigned immediately after Maurice's ousting by the Saatchi group in 1995 and subsequently helped to establish their rival agency.