The knitted fabrics which are used in the manufacture of sportswear should be fitting to some parts of the body with enough stretch-ability; namely the breast area including the under-arms. Herein, we adopt CLO3D simulation system to assign the proper blending ratio and fabric weight of selected bio-treated knitted polyester/Lycra (PET/L) blended fabric for manufacture of sportswear. Three different blending ratios (96/4, 94/6 and 92/8) with three different fabric weights; light (160 g/m2), medium (200 g/m2), and heavy (250 g/m2) of PET/L knitted fabrics were fabricated. These fabrics were bio-treated with the lipolytic enzyme Lipolase 100L-EX to enhance the fabric hydrophilicity and to reduce the accumulation of electrostatic charge on the fabric surface without severe loss in fabric weight and burst force. Results of this investigation revealed that the light and medium weight bio-treated PET/L (92/8) knitted fabric exhibited the highest hydrophilicity and lowest electrostatic charge; thus they have been selected for evaluation by CLO3D simulation system. The selected bio-treated samples were found to have appropriate fitting (pressure) and stretch-ability at the shoulders, under-arms, and breast areas of a soft bra usually used in some women's sportswear. Bio-treatment of the said fabric with Lipolase 100L-EX had no significant effect on the fabric thickness and air permeability. The polyester component of the bio-treated PET/L knitted fabrics was found to be dyeable with the cationic dye C.I. Basic Red 18. The scanning electron microscopy revealed no deterioration in bio-treated knitted fabrics which assures that the used lipase enzyme is a benign reagent for activation of the polyester fibre surface.