Kozo Tashima was born in the Amakusa District of Kumamoto Prefecture in 1957. While at Urawa-Minami High School and the University of Tsukuba, he won the All Japan Soccer Tournament. He joined Furukawa Electric and played in the Japan Soccer League, becoming a representative forward for the Japan national team. He coached the Japan U-17 and U-19 national teams and served as the national technical director, general secretary and vice president of the Japan Football Association prior to assuming his current position. He has served in his current position since March 2016. Additionally, Tashima has been a member of the Federation of International Football Association since 2015 and vice president of the Japanese Olympic Committee since 2019.