Toshiyuki Hosokawa was born in Fukuoka, Japan in 1940. He began his acting career when he joined the Bungakuza theatrical troupe after leaving Gakushuin University.
Hosokawa's earliest credits come from the 1960s, with roles in theatrical films. During that decade, he had roles in Warm Current in 1966, Zatoichi Breaks Jail in 1967, Namida gawa in 1967, Impasse in 1967, Fight for the Glory in 1969, Eros Plus Massacre in 1969, and Sworn Brothers in 1969.
His film career continued in the 1970s, with roles in Zatoichi Meets Yojimbo in 1970, Confessions Among Actresses in 1971, Ongaku in 1972, Miyamoto Musashi in 1973, and Sono go no jingi naki tatakai in 1979. The 1970s also saw Hosokawa expand into television, with roles in such series as Akuma no youna aitsu in 1975, Kaze to kumo to niji to in 1976, Mu ichizoku in 1978, and Necchu jidai: Keiji hen in 1979. In 1970, Hosokawa also starred in the Japanese production of the musical Show Girl; he stayed with this production for 15 years.
Hosokawa tried his hand at voice acting in 1980 and 1981, by providing the voice for Tohru Rikiishi in the Tomorrow's Joe anime film from 1980, as well as the 1981 sequel, Tomorrow's Joe 2. He also had roles in a couple of theatrical films during that decade: The Makioka Sisters in 1983 and New Morning of Billy the Kid in 1986.
Hosakawa's credits from the 1990s include theatrical films, television series, and television movies. He made appearances on the big screen in Shonen jidai in 1990, Tobu yume wo shibaraku minai in 1990, Yonigeya hompo 2 in 1993, and Raijo no jikan in 1997. For television series, Hosakawa had roles in Ude ni oboe ari in 1992, If: Moshimo in 1993, Hachidai shogun Yoshimune in 1995, and Mori Motonari in 1997. He also appeared in the television movies Jujiro ni tatsu onna in 1991 and Araki Mataemon: Otokotachi no shura in 1994.
Hosakawa only had a few roles in the 2000s. His only theatrical film appearance was in Departing Osaka Station at 0:00 in 2006. For television series, he appeared in Aoi tokugawa sandai in 2000, Henshu-oh in 2000, and Mayonaka wa betsu no kao in 2002. He also had a role in the television movie Shinano no koronbo jiken fairu 4: Togurashi densetsu satsujin jiken in 2003. In 2004, Hosakawa began serving as a professor at the Osaka University of Arts.
On January 12, 2011, Hosokawa fell in his living room and suffered a concussion, and was taken to a hospital in Tokyo. Toshiyuki Hosokawa passed away on Friday, January 14, 2011 from an acute subdural hematoma. Hosokawa was 70 years old at the time of his death.