The success of the Panzerjäger I gave the German Army the experience of mounting a more powerful anti-tank gun on an existing chassis, this resulting in the Marder I. The chassis chosen was that of the French-designed Tracteur Blindé 37L of which large stocks were made available after the fall of France. The 37L hull was mostly unchanged aside from the replacement of its load platform with a superstructure for the gun. Like other self-propelled anti-tank designs, this was lightly armored (but slightly sloped) and had an open-topped roof. The gun used was the powerful 7.5cm PaK 40/1, a significant improvement for the 4.7cm gun in the Panzerjäger I as well as the towed 3.7cm PaK 36s that were the most widely used by the Army but which were often too weak to penetrate the thick sloped armor of Soviet tanks after Barbarossa. Marder Is were issued to panzerjäger detachments beginning in 1942, mostly in France, but the low number of conversions resulted in it having a minimal impact on the war. Nevertheless, it was the first in a trio of conversions that eventually led to more powerful anti-tank vehicles used during the second half of the conflict.

The Marder I (SdKfz 135) was designed by Alfred Becker and ordered in May 1942, with conversions taking place between July and August of that year. There were no variants.