At a very young age, Seagal lied about his age and got a job as a dishwasher at a restaurant named The Wagon Wheel. One of the cooks at the restaurant was a Japanese shotokan karate expert and noticed Seagal moved very quickly around the kitchen. He taught Seagal the basics of karate. Seagal began training in aikido under master Harry Kiyoshi Ishisaka, founder of the Orange County Aikido School (Orange County Aiki Kai) (OCAK) in 1964. Seagal considers him to have been the most important martial arts teacher in his life. Seagal moved to Japan in his late teens after he went to Japan with his father who was visiting for military purposes and met karate masters and decided to remain in Japan. He received his 1st dan degree (Shodan) under the direction of Koichi Tohei. He continued to train in aikido as a student of Seiseki Abe, Koichi Tohei (whose aikido organization, Ki Society, Seagal refused to join in favor of staying with the Aikikai), Kisaburo Osawa, Hiroshi Isoyama and the second doshu Kisshomaru Ueshiba. He attained a 7th dan degree and Shihan in aikido and became the first foreigner to operate an aikido dojo in Japan.[9] Seagal claims to have been subject to xenophobia in Japan and visited by many Japanese coming to try to kill him, resenting his teaching the Japanese.[citation needed]

When Seagal's father-in-law retired from his job as an instructor, Seagal became the new head of the organization known as Tenshin Aikido in Jūsō, Osaka City (affiliated with the Aikikai). Seagal is known by his students as Take Sensei. When Seagal left his dojo in Osaka, his then-wife Miyako became the caretaker of the dojo which has continued to the present day. Seagal initially returned to Taos, New Mexico, with his student (and later film stuntman) Craig Dunn, where they opened a dojo, although Seagal spent much of his time pursuing other ventures. After another period in Japan, Seagal returned to the U.S. in 1983 with senior student Haruo Matsuoka. They opened an aikido dojo, initially in North Hollywood, California, but later moved it to the city of West Hollywood. Seagal left Matsuoka in charge of the dojo, which he ran until the two parted ways in 1997.