The Moroccan olive oil industries generate a substantial amount of olive mill wastewater (OMW), causing a significant environmental issue. Consequently, its valorization represents a sustainable agroecological solution to the environmental problems caused by this uncontrolled discharge. In this context, the use of OMW as an organic biofertilizer in agriculture has been suggested as an alternative to restore soil fertility and improve agricultural production. To comprehensively understand its impact, our study focused on the local cultivar (Vicia faba L.), investigating the consequences of daily applications of OMW at varying doses (5%, 10%, 20%, 30%). In our experimental design, NaCl solutions, mimicking the electrical conductivity of OMW, were used to pinpoint potential phytotoxic agents within the wastewater. The results revealed that a high dose of OMW had significant effects on morphological, physiological, and biochemical parameters. Additionally, phytotoxicity depended on both OMW concentration and the growth stage of (Vicia faba L.), causing growth delays, germination inhibition, and the accumulation of proline and soluble sugars. These findings underscore the complexity of using OMW in agriculture and highlight the critical importance of precise control over application rates for the success of this approach. While reusing OMW presents a viable and practical solution, a nuanced understanding of its impact on specific crops and a meticulous approach to dosage management are imperative to realize its potential benefits and mitigate any potential risks to crop productivity.