Pet chameleon size varies depending on the species of chameleon. The three most popular chameleon species include the veiled chameleon, Jackson’s chameleon, and the panther chameleon. The largest is the panther chameleon, growing up to 20 inches in length. The veiled chameleon is similar in size, growing up to 18 inches in length. Jackson’s chameleons stay smaller, usually growing to about 9 to 13 inches.