The event, also known as the Laughter Fair, runs until Thursday and features meetings, workshops and contests, among other activities.
Clowns will compete at inflating balloons, acting, performances for children, the champion of champions event and the five-minute routine.
Mime, juggling, children's games, bands, costume and make-up competitions are also being held.
Clowns from Peru, El Salvador, Honduras, the Dominican Republic, Guatemala, Belize, the United States and Mexico are attending the convention, where they can discuss their experiences at meetings and workshops.
One of the most anticipated events is the parade of clowns through the streets of Mexico City on Wednesday.
The conventioneers will attempt on that day to break their own world record of 15 minutes of continuous laughter.