Clash, 52, resigned last November from Sesame Workshop amid the scandal.
U.S. District Judge John Koeltl ruled the claims were filed too late for him to consider, The Hollywood Reporter said.
New York state law stipulates this type of lawsuit must be filed within six years of the event or three years after a plaintiff turns 21.
The alleged victims said their relationships with Clash occurred in the 1990s and 2000s when they were in their early or mid teens.
Clash, who provided the voice of furry red monster Elmo on the children's program for more than 20 years, won three Daytime Emmy Awards for his work on "Sesame Street" last month.