In 1939, the T-26 was further improved.
A new turret, closely related to the original type, was introduced having a new cast or drop-forged forward section which made for easier assembly.
The two additional 7.62mm Degtyarev DT machine guns (rear and top) were more uncommon compared to the Model 1938 welded turret.
In addition, the hull was redesigned with a new upper superstructure which was wider, better armoured and had angled sides for better protection. This also permitted increased fuel and ammunition stowage.
Due to fatal experiences with »Molotov cocktails« thrown onto the engine deck during the Spanish civil war, the engine ventilators were now protected by a rounded top shield.

The Model 1939 was the last main production series of the T-26 with some 1,300 vehicles manufactured until 1940.
During the course of the war in Finland, it quickly became apparent that the T-26 was too thinly armoured to resist contemporary anti-tank guns, or even modern anti-tank rifles.
As a result, a small number of the Model 1939, also called »T-26S«, were rebuilt with added turret and hull armour bringing the thickness to 50mm.
These were called the »T-26E« (»s ekranami«: with applique).