The National Highway Traffic Safety Administration said the Prius vehicles made between March 31, 2009, and Oct. 9, 2009, were involved in the recall as were Lexus HS250h vehicles made between June 19, 2009, and Oct. 9, 2009.
"Nitrogen gas from a component of the brake booster pump assembly could leak into the brake fluid," the NHTSA said in a statement.
This could reduce the hydraulic pressure that operates the brakes, which increases the risk of a crash, the regulator said.
The recall is scheduled to begin in late July. Toyota said it would replace the affected brake booster pump assemblies.
Consumers can call 800-331-4331 for information.