Eric Justin Toth, also known as David Bussone, was a third grade teacher at the National Cathedral's Beauvoir school in Washington, D.C., in 2008 when pornographic images were found on a school camera that had allegedly been in his possession.
Toth, 30, is 6 feet, 3 inches tall, weighs approximately 155 pounds and has brown hair and green eyes.
The FBI issued a wanted poster with several photos of the suspect.
The agency described Toth as a computer expert who has above average knowledge of the Internet.
He graduated from Purdue University with an education degree and the FBI poster says "he may advertise online as a tutor or male nanny."
According to the FBI, since he left the Washington area, Toth is believed to have traveled to Illinois, Indiana, Wisconsin and Minnesota.
He was last seen in a homeless shelter in Phoenix.
The FBI hopes adding Toth to the most wanted list and offering a reward of up to $100,000 will bring in new tips and lead to his arrest.
An FBI statement notes the former teacher has eluded capture despite various media reports about the case and his being featured on the "America's Most Wanted" television program.
Toth is the 495th person to be put on the FBI's Ten Most Wanted Fugitives List, which was created in 1950.
The FBI says 465 of those fugitives were found, 153 of them as a result of help from the public.