The main objective of this study is to evaluate the potential of olive mill wastewater (OMW) as an organic fertilizer through co-composting with various agricultural by-products. OMW was mixed with agricultural by-products, including maize silage, sugar beet pulp, and sugarcane bagasse, in controlled proportions and conditions. The study was conducted at the National Institute of Agricultural Research in Rabat, Morocco. The composting process was monitored over time, focusing on the evolution of key physicochemical parameters and phenol content of each mixture. The results showed that the performance of the composts varied, with the mixture containing sugar beet pulp (SBPO) exhibiting the most promising results, followed by maize silage (MSO) and sugarcane bagasse (SBO). These results suggest that co-composting OMW with agricultural by-products can produce high-quality organic fertilizers, thus reducing the need for inorganic alternatives and providing a sustainable waste management solution in the olive oil industry. It highlights the potential for reducing phenols characteristic of OMW and promoting sustainable agricultural practices. The application of the composts to crops was not tested, highlighting the need for further research in this regard. Future investigations should focus on evaluating the long-term effects of OMW-derived composts on soil health and crop productivity. This study explores a combination of materials that, to our knowledge, has not been previously documented in scientific literature. The results underscore the importance of sustainable waste management practices and their potential role in improving soil fertility and reducing the environmental impact associated with olive oil production.