The Wall Street Journal first reported the takeover offer Friday, citing unnamed sources. It said that terms of the possible deal were not available and that the offer could go nowhere.
When contacted by a Times reporter Friday, Hasbro and Mattel declined to comment on the report.
A tie-up between Hasbro and Mattel would put brands including Barbie, American Girl, G.I. Joe and Nerf under the same roof. Mattel has struggled with slumping sales despite the entrance earlier this year of new Chief Executive Margo Georgiadis, a former Google executive who was expected to bring her digital know-how to the toy maker.
In late October, Mattel reported a 14% drop in its third-quarter sales, excluding the effect of currency fluctuations, and suspended its quarterly dividend. It blamed some of the decline on the recent bankruptcy filing of retailer
Mattel shares rose 20.7% to $17.64 on Monday. They are still down 36% this year.
Hasbro shares rose 5.9% on Monday to $96.84.
Times staff writer James F. Peltz contributed to this report.
4 p.m.: This article was updated with Mattel shares' closing price.