The production of hot w ater dip hydrolysate (HWDH) from tilapia (Oreochromis niloticus) with DH of 25.43% improved its bioactivity. A pressure-driven ultrafiltration (UF) membrane separated HWDH based on molecular weight cut-offs (MWCO) of 1000, 3000, and 5,000 Da, to produce fractions F1-k, F3-k, F5-k respectively and 5k-R (retentate of 5,000 Da) with antioxidative activity. The UF produced permeates with smaller Mw distribution (177-3015 Da), with F1-k portraying lowest molecular weight range (180-2008) Da), whilst the retentate fraction ranged higher 179-8130 Da. The antioxidant efficacy of fractions with ABTS, DPPH, inhibition of linoleic acid autoxidation, Metal-chelating ability, and reducing power exhibited antioxidant activity (82.30% ) for F1-k, within range of "-tocopherol (87.04%) and BHT (89.71%) in linoleic acid oxidation system. Furthermore, F1-k exhibited higher ABTS, DPPH and M etal-chelating activity with a significant difference (p<0.05). The correlation between the smaller Mw size and antioxidant activity is superiorly exhibited in the F1-k fraction.