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Messinian gypsum deposits from Dir El-Baraqan area, Northern Coast of Egypt, were investigated by stable sulfur isotope method, X-ray diffraction, infrared spectroscopy, optical microscopy, and scanning electron microscopy to differentiate features formed under substantial microbial influences as indicator of paleoenvironments. Petrographically, gypsum deposits were classified into three types: biolaminated gypsum, disordered selenite, and swallow-tail selenitic crystals. Biolaminated gypsum is characterized by regular alternating dark and light laminae, which were formed due to the seasonal environmental changes in Dir El-Baraqan area. Stable sulfur isotope data show that the gypsum deposits are characterized by delta S-34 values ranging from +18.1 to +28.1 aEuro degrees. In swallow-tail gypsum, the delta S-34 values are characterized by a narrow range (from +20.0 to +20.2 aEuro degrees) which is considered as the primary phase. In biolaminated gypsum, the delta S-34 values ranged from +22.8 to +28.1 aEuro degrees which is considered as the secondary phase. However, the white laminae are characterized by delta S-34 values ranging from +22.8 to +24.1 aEuro degrees, while dark laminae are characterized by delta S-34 values ranging from +27.2 to +28.1 aEuro degrees. The high delta S-34 values of dark laminae revealed the increasing activity of sulfate-reducing bacteria.