Frundsberg was born to Ulrich von Frundsberg and his wife Barbara von Rechberg at Mindelheim, into an old line of Tyrolean knights who had settled in Upper Swabia. He fought for the Holy Roman Emperor Maximilian I against the Swiss in the Swabian War of 1499, and in the same year was among the Imperial troops sent to assist Ludovico Sforza, Duke of Milan, against the French. Still serving Maximilian, he took part in 1504 in the war over the succession to the duchy of Bavaria-Landshut, fighting against the Pfalz-Counts Philipp and Ruprecht. He distinguished himself during the Battle of Regensburg. Maximilian I personally bestowed knighthood on him. Later, he also fought in the Netherlands.