Around 1,250 customers of online brokerages were asked during the fourth quarter of 2011 to rate their levels of satisfaction with the firms on a 100-point scale. Overall satisfaction fell 2.6 percent from the previous year, to 76, according to the study by the American Customer Satisfaction Index.

"Despite efforts by brokerages to improve their websites for making and recording transactions, market performance plays a large role in determining investor satisfaction," said Claes Fornell, founder of ACSI.

U.S. equity markets ended 2011 largely flat after a roller-coaster year fueled by uncertainty surrounding the economic recovery, a downgrading of the U.S. credit rating, and the debt crisis in Europe.

Three brokers tied for the top spot in the study at 79: Charles Schwab Corp, E*Trade Financial Corp and Fidelity. Next was TD Ameritrade with a 78. Beyond the top four brokers, the "all others" category, which includes Vanguard and Scottrade, came in at 75.

New York-based E*Trade showed the biggest improvement from the year before, up 3.9 percent. Schwab slipped 1.3 percent, while Fidelity and TD Ameritrade both gained 1.3 percent. The "all others" category was down 3.8 percent.

(Reporting By John McCrank in New York; Editing by Walden Siew and Matthew Lewis)

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