Underlying net income, which excludes the impact of interest rates and equity market movements, fell about 10 percent to C$554 million ($424 million), or 90 Canadian cents per share, in the quarter ended June 30.
Analysts on average were expecting earnings of 92 Canadian cents per share, according to Thomson Reuters I/B/E/S.
Sun Life's total benefits and expenses soared to C$8.9 billion from C$687 million.
The company's underlying net income in Canada fell 20 percent to C$200 million, while underlying net income from its U.S. business rose 8.6 percent to C$114 million.
Net income fell nearly 34 percent to C$480 million, or 78 Canadian cents per share, hurt by low interest rates and market volatility due in part to Britain's vote to leave the European Union.
Manulife Financial Corp (MFC.TO), Canada's biggest life insurer, reported a lower-than-expected quarterly profit last week, also blaming interest rates and Brexit-driven market volatility.
Reporting by Matt Scuffham in Toronto and Arathy S Nair in Bangalore; Editing by Savio D'Souza