A native of Yokkaichi, Mie, Okada graduated from the University of Tokyo with a degree in law, and entered the Ministry of International Trade and Industry.

[4] Okada ran for the House of Representatives at the 1990 general election from LDP, representing Mie Prefecture's third district, and later joined the Takeshita faction of the Liberal Democratic Party, and followed faction leaders Tsutomu Hata and Ichirō Ozawa to join the Japan Renewal Party in 1993.

Ichirō Ozawa, however, whose resignation had also been reported announced by Hatoyama, was still supporting another less well known possible successor, Shinji Tarutoko, 50, a legislator who leads the environmental policy committee in the lower house of Parliament, a day before the DPJ leadership elections.

[9] As foreign minister, Okada was one of the chief participants in negotiations with the United States (US) over the relocation of Marine Corps Air Station Futenma on Okinawa.

[9] In a September 2010 cabinet reshuffle, Okada was moved from foreign minister to secretary general of the DPJ.

[12] Okada ran in the DPJ leadership election held in January 2015 after former president Banri Kaieda resigned after losing his seat.

He was many times interviewed by Sekai Nippo, the official newspaper of the Unification Church, an anti-communism new religion.