Kostadin Alakushev was born in the village of Tarlis, in the Ottoman Empire, that is now in Greece known as Vathytopos, Kato Nevrokopi municipality, Drama regional unit.

He graduated from the Bulgarian Men's High School of Thessaloniki and afterwards worked as a teacher in different villages in the region of Nevrokop and Ser.

He became a member of the IMARO and participated in the Ilinden-Preobrazhenie Uprising in the revolutionary band of Stoyan Malchankov.

In 1909 he participated in the foundation of a chapter of the People's Federative Party (Bulgarian Section) in Nevrokop.

In 1912, Alakushev was kidnapped together with Stoyko Pashkulev and Blagoy Meterov and killed in the vicinity of the village of Fotovishta (today known as Ognyanovo).