The recall covers Boulevard 70-G3, Advocate 70-G3 and Pavilion 70-G3 models sold in the U.S. and Canada.
U.S. regulators say the seats were made with softer chest pad material that can be bitten off and chewed by children.
Britax says in a letter to the government that it has three reports of children biting off pieces and gagging on them.
The seats were made from June 11 to Aug. 31.
Britax will send new pads for free to about 3,000 people who registered seats. Other owners can call (888) 427-4829.
The seats can be used without pads until new ones arrive.