The toy companies are reported to have been in on-and-off discussions about a possible merger.
Hasbro approached Mattel about a potential transaction late last year, and the companies have held sporadic talks about a deal.
There have been no details of how a transaction might be structured, and the talks may not lead to a deal.
Shares in Mattel jumped 8% on Thursday following the report of the potential merger.
This is not the first time a combination has been talked about. In 1996, Mattel made a $5.2bn (£3.5bn) offer to buy Hasbro, but the two sides failed to reach a final agreement. Should a deal succeed this time around, it would bring together Mattel’s strength in the girls category and Hasbro’s dominance over the boys’ toy aisle, while making the combined company a stronger competitor to Lego.
According to Jaime Katz, an analyst at Morningstar, if combined, the companies would have around a quarter of the market in the US. Another hurdle to consider would be merging cultures and headquarters on opposite US coasts, Katz said.
Representatives for Hasbro and Mattel have declined to comment.