In the so-called "say-on-pay" referendum, 63.6 percent of votes were cast to approve 2015 compensation awards, according to a preliminary count announced by the company at its annual general meeting in Miami.

Proxy advisory firms Institutional Shareholder Services Inc and Glass, Lewis & Co had recommended investors vote against approving last year's payouts to executives.

The firms had said it was wrong for CEO Mike Corbat to have received a 27 percent increase in annual compensation, which boosted his total for 2015 to $16.5 million, even though the bank's shareholder returns have lagged competitors.

Directors had said that Corbat delivered more improvements in company financial performance than were shown in the stock price in 2015. They also said Corbat's pay should rebound from having been docked the year before because of past regulatory capital issues and fraud in a business in Mexico.

In another vote, only 3.5 percent of votes cast favored a breakup study of the bank, which is the fourth biggest in the United States by assets.

Chairman Mike O'Neill said at the meeting that the company's strategy for its size and scope is based on extensive analysis, including three major studies over the past seven years. Corbat said Citigroup's scale and business mix contribute to annual "operating efficiencies" of $8 billion to $12 billion.

(Reporting by David Henry in New York Editing by W Simon)