Kevin Kiadii, 25, said he was 16 when he met Clash, 52, on a gay phone chat line. According to the lawsuit, Clash initiated contact, sent a luxury car to bring Kiadii to his New York apartment "gave Kiadii alcohol and groomed him with attention and affection."
The lawsuit says the sex was consensual, but the age of consent in New York is 17.
"As a 16-year-old child, Kiadii was not emotionally or psychologically prepared for a sexual relationship with a grown man in his forties," the lawsuit says.
Kiadii is represented by attorney Jeff Herman, who is also representing four other men with similar allegations. Each of the five suits argue the same thing: that the sex was consensual but the plaintiffs were not old enough to consent or understand the relationships.
"The allegations in this lawsuit follow the same pattern we've seen before," Herman said in a statement.
"Each of these victims alleges that Kevin Clash was a father figure who groomed them with attention before engaging them in sexual contact. By coming forward and standing up for his 16-year-old self, Kevin Kiadii has taken the first step in his healing process."
Clash, who has denied the allegations repeatedly, resigned from Sesame Street in November after a second accuser came forward and filed the first lawsuit.
Clash's attorney, Michael Berger, has called on a New York judge to toss the previous lawsuits, saying the cases are "meritless."