The insurer is working with advisers to evaluate a sale, a process that is at an early, informal stage, said the people, who asked not be identified because the matter isn't public. No decision has been made and MassMutual could opt to hold onto the firm, they said.
A representative for MassMutual declined to comment.
The potential sale comes as asset managers grapple with narrowing margins as fees fall and regulatory costs mount. Firms such as Oppenheimer that focus on actively managed funds have also been steadily losing business to so-called passive vehicles such as index funds, which are cheaper.
Those pressures have analysts expecting more industry consolidation as large and midsize money managers look for scale and diversity to boost sales.
MassMutual, which acquired OppenheimerFunds in 1990, has been shedding businesses and relocating employees around the U.S. as CEO Roger Crandall seeks to reshape the company. The life insurer is among the largest and most prominent in the U.S. that is owned by its policyholders rather than stockholders.
OppenheimerFunds managed more than $249 billion as of the end of July, according to its website. It specializes in mutual funds, but has been expanding into exchange-traded funds in recent years to diversify and boost fees.