Born in Germany to a religiously observant family, Amichai and his family emigrated to Eretz Yisrael in 1935, living briefly in Petach Tikvah before settling in Jerusalem. In World War II he fought with the Jewish Brigade of the British Army, and upon his discharge in 1946, he joined the Palmach. During the War of Independence he fought in the Negev, on the southern front. Following the war, Amichai attended Hebrew University, studying Biblical texts and Hebrew literature, and then taught in secondary schools.