For his first climbing season, Jean Couzy chose in 1946 to go to the Austrian Alps. In 1948, he returned to the Pyrenees where he made the Pic des Crabioules for the first time. The same year and the following years, he assiduously frequented the Dolomites where he repeated renowned routes or made first ascents. It also repeats great races and opens up new routes in the Western Alps. Jean Couzy is also one of the first to open difficult routes on the limestone walls of the Pre-Alps.
Jean Couzy takes part in several expeditions in the Himalayas. In 1955, he made with Lionel Terray the first ascent of Makalu, the fifth highest peak in the world (8,463 m). Five years earlier, Jean Couzy had already been part of the French expedition led by Maurice Herzog to Annapurna, the first of fourteen peaks over 8,000 meters climbed.
Jean Couzy pursues his career as an amateur mountaineer while continuing his professional career in the Air Force and without sacrificing his family life (he is married and has four children). He is interested in the classification of difficulties and the history of mountaineering; he is in charge of the Alpine Chronicle which presents the new climbs in the Club Alpin FranΓ§ais magazine, "La Montagne". Jean Couzy's approach to the risks inherent in the mountains is rational. He wants to be careful and refuses, for example, to go mountaineering alone.