Mattson is recognized as the “Father of Uechi-ryu karate” in America. Mattson was originally taught by Tomoyose Ryuko after hours on the military base on Okinawa while serving in the U.S. Army. He was also trained at the Uechi-Ryu Karate-Do headquarters by Kanei Uechi. Mattson was promoted to 1st degree black belt before leaving Okinawa at the end of his service in the military.

Mattson was the first to teach Uechi-ryu professionally in the USA, resulting in the majority of the growth of the system. He began teaching Uechi-ryu in Boston, Massachusetts in 1958 and ran the Mattson Academy in Boston and other locations for decades. Many of his students, upon mastery of Uechi-Ryu karate, started successful karate schools in the New England area and around the world. He currently teaches at the Mattson Academy (Shubukan) in Florida and online (athomekarate.com). Mattson pioneered the use of online karate, introducing his “virtual dojo” coaching system 20 years ago.

He has sponsored many seminars by karate masters from around the world including Okinawa. In addition, Mattson hosts Winterfest in Florida each year where international Uechi-ryu practitioners as well as other martial artists come to share their knowledge and techniques.

Mattson was one of the first to publish a book in English about karate; and has written a number of books about Uechi-ryu, including:

• The Way of Karate, Tuttle Publishing, 1958
• Uechi-ryu Karate Do : Classical Chinese Okinawan Self Defense, Peabody Publishing, 1974
• The Black Belt Test Guide, Peabody Publishing, 2008
• The Way of Uechi-ryu Karate, Peabody Publishing, 2010