The olive mill waste water, effluents from the trituration of olives, are treated in most Mediterranean countries by natural evaporation. However, this method of treatment is a source of air and soil pollution by the generation of a solid waste, called olive mill waste cake. This work focused on the extraction of vegetable oil from this by-product for the production of biodiesel by transesterification. The extraction took place with a Soxhlet extractor, using hexane as solvent. The vegetable oil and biodiesel were characterized by measuring the physicochemical parameters that identify them according to AFNOR standards. The extraction results show that the oil yield is 21.28%. The oil obtained is characterized by density, water and ash content, acidity, saponification, peroxide and ester indices in accordance with NF EN ISO 3838 2004, NF V 03-921 2010, ISO 21656 2021, NF EN 14104 2021, NF EN ISO 365 2020, ISO 3960 2017 and NM ISO 7660 2016 respectively. The yield of the oil esterification reaction is 86.41% 403.64106 MJ/tons of olive mill waste cake. The biodiesel produced is comparable to petroleum diesel according to EN 14214, 2013. The yield of the oil esterification reaction is 86.41% or about 185 Kg of biodiesel/ton of olive mill waste cake, and in terms of energy 2783.7 MJ or 2 GW/t. The biodiesel produced is comparable to petroleum diesel according to EN 14214,2013.