Behaim first visited Portugal about 1480 as a merchant in the Flemish trade and, claiming to have been a pupil of the astronomer Johann Müller (Regiomontanus) at Nürnberg, became an adviser on navigation to King John II. He may have introduced the astrolabe of brass to replace wooden models of this instrument, then used in navigation to ascertain the altitudes of the Sun, Moon, and stars in order to deduce time and latitude. He probably voyaged down the west coast of Africa (1485–86) with Diogo Cão.

Returning to Nürnberg (1490), Behaim began constructing his globe with the help of the painter Georg Glockendon and finished it in 1492. In view of the extent of Portuguese exploration, his depiction of the world was surprisingly inaccurate and out of date, especially in relation to the west coast of Africa. It is interesting, nevertheless, for the indication it provides of common geographic suppositions on the eve of the discovery of North America. His globe is in the collection of the German National Museum in Nürnberg.