The convention, starting Monday at the LaGuardia Plaza Hotel, features face-painting competition and lessons on balloon sculpture-making and honker-creation, the New York Daily News reported.
Organizers said about 30 clowns are slated to visit young and elderly patients at three city hospitals Wednesday.
Dennis DiMartino, 52, who performs under the name "Cappy Da Clown" at Brooklyn Cyclones baseball games, said he is organizing city tours in school buses for visiting clowns.
"I'm trying to put a red nose on the front of the bus," he said. "But I haven't figured out how yet."