The man, who remains anonymous, sued Clash Tuesday for unspecified damages, saying the puppeteer met him in New York after trolling gay telephone chat lines seeking underage boys for sex.
Clash resigned last week after 28 years with Sesame Street.
The latest accuser, now 29, said he was exploring modeling opportunities in New York at the age of 16 when he met Clash on a chat line in 2000.
Clash's attorney says "the lawsuit has no merit."
The Associated Press contributed to this report.