Frank Nagai was born in Matsuyama, Miyagi, Japan. He had his major debut in 1954 when he was discovered by composer Tadashi Yoshida (吉田 正). He had many hit songs such as Yurakucho de Aimasho, Tokyo Night Club, Kimi Koishi, and Omae ni. He also appeared in motion pictures, including the film Nishi Ginza Eki Mae (1958), for which he sang the title song.
He enjoyed immense popularity as a singer in Japan. He is credited with discovering female singer Kazuko Matsuo (松尾 和子), who later became quite famous. The two often sang duets together.
He attempted suicide on October 21, 1985, attempting to hang himself, distressed that his lover bore his illegitimate child. He survived, but was left with permanent brain damage.