Abstract <p>This study tested the hypothesis that controlled irrigation with olive mill wastewater (OMW) enhances legume growth while providing an ecological alternative to uncontrolled effluent disposal. The effects of three doses of raw OMW (25, 50, and 100 m³/ha) on two Mediterranean species, faba bean (<i>Vicia faba</i>) and pea (<i>Pisum sativum</i>), were evaluated through agro-physiological parameters (chlorophyll fluorescence, leaf chlorophyll content, total nitrogen) and biochemical markers (proline, soluble sugars, polyphenols), compared to an untreated control. Results revealed a positive correlation between OMW doses and chlorophyll accumulation (15.02% in pea at 50 m³/ha) and nitrogen content, indicating improved photosynthetic activity and nutrition. A marked increase in total phenolic compounds (53.65%) and in proline content (65.11%), a key osmoprotectant, was observed in faba bean at 100 m³ ha^–1, suggesting an adaptive response to physiological stress induced by OMW organic compounds. Biochemical changes and calcareous soils show OMW’s potential as a fertilizer and irrigation source. This is the first evidence of polyphenols and osmoprotectants protecting legumes from OMW, which could reduce the Mediterranean olive oil industry’s environmental impact.</p>