The present study concerns the oceanic anoxic event of the lower Toarcian and its consequence on the morphology of benthic foraminifera in the pre-Atlas domain in Algeria. This study is complementary and current because there has been no previous study in this area on this event, that would confirm its paleoenvironmental globality. The section was located NW of the village of Bénia in Tiaret in the Nador mountains. It has a thickness of 20 m of a marl–limestone succession and is composed of two main members of upper Domerian to lower Toarcian age. The vertical succession of benthic foraminifera allowed us to find a zone of total absence of foraminifera at the level of the Polymorphum–Levisoni transition zone. This succession is characterized by the predominance of Nodosarids in the Polymorphum zone, and the proliferation of coiled forms precedes the anoxic zone. The geochemical analysis of the TOC shows an organic carbon rate greater than 2.5% in the same zone of the absence of foraminifera, and a negative excursion of δ13C. The isotopic correlation of these data with others from the two basins of western Algeria (Tlemcenian domain, Atlas domain) shows a simultaneity of anoxia and differentiation of the intensity of this event. According to the results of this study, it was concluded that the oceanic anoxic event of the lower Toarcian is a global event at different degrees, and the morphological behavior of benthic foraminifera evolves according to the existence and absence of oxygen in the environment.