After graduation, Kōmura passed Japan's bar exam and then immediately entered politics. He was first elected to the House of Representatives in the June 1980 election, and has been re-elected in each election since then. He became Director-General of the Economic Planning Agency (as a Minister of State) in June 1994, Minister for Foreign Affairs in July 1998, and Minister of Justice in December 2000. In August 2007, under Prime Minister Shinzō Abe, he became Minister of Defense.[3] Kōmura leads a small faction of the LDP named after himself and ran for LDP president in 2003, but was defeated by Junichirō Koizumi.[4]
Following Abe's resignation in September 2007, Kōmura became Minister for Foreign Affairs for a second time on 26 September 2007, in the Cabinet of Prime Minister Yasuo Fukuda.[5] He remained in that post until he was replaced by Hirofumi Nakasone in the Cabinet of Tarō Asō, appointed on 24 September 2008.[6] He is vice president of the LDP.[7]