Several trials with Pleurotus pulmonarius mushroom were carried out in liquid state cultures, in synthetic media containing commercial glycose and olive mill wastewater (OMW) with phenolics concentration adjusted to 10% and 30% v/v. Results demonstrated that at the end of fermentation period the phenolic content reduction was very high (93-95%), as well as substrate decoloration, with values ranging from 70% to 85% (medium containing 10 and 30% v/v phenolic compounds respectively), indicating the great capability of Pleurotus strains for OMW detoxification. Moreover, the highest phenolic concentration (30% v/v) affected positively biomass and intra-cellular polysaccharide (IP) production, reaching 30.61 g/L and 4.30 g/L, respectively. On the other hand, although lower values of biomass and IP in absolute values were synthesized in the medium with 10% v/v phenolic compounds (22.66 and 3.92 g/L respectively), the amount of IP in relative values was as high as 20 w/w. The maximum anti-oxidant activity (expressed as total phenolic compounds) of 0.4 g/L was also determined in P. pulmonarius biomass produced in the medium with 10% v/v phenolics. In conclusion, the examined mushroom species could be used with great success as a mean of biological treatment of OMWs with simultaneous production of high nutritional value products (biomass, polysaccharides, phenolic compounds).