Leu presumably trained with his father, Hans Leu the Elder, in Zurich before setting out on his journeyman's travels. He is documented in Albrecht Dürer's workshop in Nuremberg in 1510. Around 1513 or 1514 he possibly worked in the workshop of Hans Baldung Grien in Freiburg, where he may have worked on the 'Schnewlin Altar' for Freiburg's cathedral. Around 1514 or 1515 Leu returned to Zurich. Owing to the iconoclastic policies of the reformer Zwingli, there were few religious commissions, so Leu was forced to make his living as a mercenary. In 1515 and 1519 he took part in the Italian campaigns, and in 1531 he fell in the Battle of Gubel, near Zurich. A large part of his oeuvre was destroyed in the iconoclasm in 1523. In addition to the few surviving paintings and woodcuts, his autonomous landscape and tree studies number among his outstanding works. Stylistically his drawings are close to those of the masters of the Danube School and Hans Baldung. Leu is considered the leading Zurich artist of his time.