Koşay was born in the village of Tilenkçi Tamak attached to the Ufa district in Russia's Idil-Ural province. After graduating from high school in 1916, Koşay became interested in ethnographic studies and, planning to study in Budapest, began to learn Hungarian. In Budapest he studied history and languages (1917–1921). He subsequently received a Ph.D. in Turkology and philology from the Eötrös College in Budapest. In 1923–1924 he took courses in ethnography at Berlin University.
Upon his return to Turkey in 1924, Koşay became involved in various government-sponsored projects related to ethnography, archaeology, and museology. Between 1927 and 1931 he created the Ethnography Museum in Ankara and served as its director. He was eventually in 1931 appointed general director of all museums and in 1945 director general of the Department of Antiquities and Museums.
Koşay's involvement in archaeological field projects began in the early 1930s. Atatürk, the leader of the then young Turkish republic, favored government-sponsored archaeological projects directed by Turkish archaeologists. He asked Koşay to excavate in the vicinity of Ankara, the capital of the republic. Thus, in 1933, Ahlatlibel, southwest of the capital, became Koşay's first archaeological project. A year later he excavated Kumtepe, near Troy. His excavations at Alaça Höyük (1935–1948, 1963–1967) revealed important aspects of Hittite and pre-Hittite civilizations in Anatolia. The site's spectacular finds earned him a reputation as one of Turkey's most experienced and knowledgable field archaeologists. During his long career, Koşay carried out numerous other excavations and field surveys: in the 1930s he excavated the Phrygian site of Pazarh in Çorum; in the 1940s, at Karaz Höyük in Erzurum and the Late Chalcolithic site of Büyük Güllücek in Çorum; in the 1960s, at the Early Bronze Age settlements at Güzelova and Pulur in Erzurum, and Pulur (Sakyol) in the Keban region; and, in 1972, at Yeniköy, also in the Keban.
Koşay published more than 35 books and 150 articles on Anatolian civilization. His work represents an important data bank on Early Bronze Age, Hittite, and Phrygian cultures in Anatolia.
- Koşay, Hamit Zübeyr. Les fouilles de Pazarli. Ankara, 1941.
- Koşay, Hamit Zübeyr. Ausgrabungen von Alaca Höyük. Ankara, 1944. .
- Koşay, Hamit Zübeyr, and Mahmut Akok. Ausgrabungen von Büyük Güllücek. Ankara, 1944. .
- Koşay, Hamit Zübeyr. Les fouilles d'Alaca Höyük. Ankara, 1951. .
- Koşay, Hamit Zübeyr, and Hermann Vary. Die Ausgrabungen von Pulur. Ankara, 1964. .
- Koşay, Hamit Zübeyr. Guide d'Alaca Höyük. Ankara, 1965.
- Koşay, Hamit Zübeyr, and Mahmut Akok. Ausgrabungen von Alaca Höyük. Ankara, 1966. .
- Koşay, Hamit Zübeyr, and Hermann Vary. Ausgrabungen von Güzeolova. Ankara, 1967. .
- Koşay, Hamit Zübeyr, and Mahmut Akok. Alaca Höyük Excavations. Ankara, 1973. .
- Koşay, Hamit Zübeyr. Keban Project Pulur Excavations, 1968–1970. Ankara, 1976. .