Cerio began martial arts training under George McCabe after being exposed to judo in the Air Force. He then studied Karazenpo Go Shinjutsu under George Pesare and received his first black belt in May 1966. Cerio opened his first martial arts school, Cerio’s Academy of Martial Arts. Through his participation in karate tournaments he came in contact with Edmund Parker. They would have a relationship that spanned nearly twenty years. After Cerio met with William Chun, Sr. (Chow’s senior student), he was granted permission to study with Chow. Cerio visited Hawaii for two weeks in the mid to late 1960s to live and study with Chow. In training, Cerio made to assume low, painful stances and throw as much as 500 weighted, full force punches. If he relaxed his stance, more punches were required. Cerio often commented on this period's influence on him and the development of his system,

During the late 1960s Cerio studied Hakkoryu Jujutsu and later received his 1st black belt (Shodan) from Larry Garron. Cerio studied Okinawan weapons and self-defense under Tadashi Yamashita, who in 1970 awarded him in 1973 a 5th black belt (Godan). Cerio studied Sil Lum kung fu under Gan Fong Chin who awarded him an 8th black belt (Hachidan) and title of Sifu in August 1973.

Cerio modified what he had learned from his limited time with Chow, Chun, Sr. Also, from his time with Pesare, and his other teachers mentioned above, and added many things from judo, jujitsu, boxing, kung fu and Shotokan. He added many kata to his system, both open-hand and weapon. Cerio incorporated variations of Shotokan forms into his system. He felt their strong stances and transitions were missing from the kenpo forms that he had been taught. Cerio can be credited with both expanding and helping to popularize kenpo on the east coast, more specifically New England. In 1989 he was given the title of professor by Thomas Burdine and was given the equivalent of his 10th dan again by Burdine but this time representing the World Council of Sokes. He founded a branch of kenpo known as 'Nick Cerio’s Kenpo' which he built up to an organization of more than 65 schools in the United States, Canada, Europe and South Africa.