The record-breaking batsman will represent the bank in a number of key Asian markets, including India and the Middle East.
Tendulkar joins a number of sporting stars who represent RBS, including the golfers Jack Nicklaus and Luke Donald, and the ex-Formula One champion Jackie Stewart.
RBS has invested heavily in its cricket sponsorship, and recently announced plans to sponsor the 2008-09 Twenty20 domestic cricket tournament in Pakistan. The bank will also sponsor the forthcoming India vs Australia Test matches, and the India vs England one-day series.