State Street Corp., one of the largest custody banks in the nation, posted better-than-expected third-quarter results as earning from managing client funds increased.

The Boston investment banking giant said it was helped by acquisitions that boosted the customer assets it services. That helped offset lower trading revenue and the impact of low interest rates, which are depressing the fees the company can charge.

State Street’s acquisitions were Intesa Sanpaolo’s securities servicing business and Mourant International Finance Administration. It said assets under custody and administration rose 13 percent from a year earlier to $20.23 trillion.

State Street’s results prompted CEO Joseph Hooley to sound a cautiously optimistic note for the full year.

"With the support of the two acquisitions, as well as strong year-to-date wins in servicing and growth in passive strategies and ETFs in asset management, we continue to expect that our operating-basis earnings per share, which exclude discount accretion, will be slightly above the adjusted operating-basis $3.32 per share recorded last year," he said in a statement.

State Street’s operating profit increased to 86 cents a share from 71-cents a year earlier. That beat analysts’ estimates of 83-cents.