Olive mill wastewater (OMW) is a by-product of olive oil production that, in its pure state, pollutes and harms the environment. We aim to minimize its polluting effect and investigate the impact of its direct application at diluted doses on soil quality and legume growth. In a pot experiment, the OMW doses of 12.5%, 25%, 50%, and 75% were applied and the growth of lentil and faba bean seedlings was studied. Fresh sampling of OMW was conducted in a modern cold extraction oil mill located in north eastern Algeria. Physicochemical properties of OMW and soil as well as plant physiological parameters are studied. The OMW used is a highly acidic effluent and rich in organic matter (56.29 ± 1.05 g/L) and mineral content (10.33 ± 0.2 g/L). The dose of 75% has significantly improved the properties of the soil by increasing its organic matter and electrical conductivity, and has also increased the leaf area of the plants. On the other hand the dose of 12.5% has improved plant height, leaf chlorophyll fluorescence, and total chlorophyll content. The research has shown that it is possible to use the OMW at diluted doses to improve soil quality in degraded land and food legume growth. Faba bean grew well in all soils treated by diluted OMW; it can be considered a tolerant plant to its pollutant effect, while lentil is sensitive and its growth is reduced by the increasing OMW dose. OMW is suitable for the vegetative development of food legumes, and it will be beneficial as a bio-fertilizer load of inorganic fertilizer used to enhance soil quality and its diluted form lessen its polluting impact on the environment and it is probably mostly important in semi-arid areas poor in organic matter.