The adjustment of material composition in fabrication of modified polymeric membrane has been considered the most efficient and easiest method. For this purpose blended membranes of high density polyethylene (HDPE)–ethylene vinyl acetate (EVA) were prepared by thermally induced phase separation method. The impact of EVA in the presence of diluent on the crystalization temperature was assessed using differential scanning calorimetry (DSC). The obtained results showed that EVA has no significant effect on the crystalization temperature of HDPE. The absorption frequencies at 1248 and 1749 cm^-1, respectively, due to C-O and C=O streching vibrations of EVA functional groups, confirmed the existence of EVA in HDPE membrane. The pure water permeability of HDPE/EVA blend was measured and compared with that of neat HDPE membrane. The results showed that an EVA content up to 2.5 wt% raised water permeability considerably and the leafy structure of the membranes contracted and the pure water permeation dropped with higher EVA content. The results of porosity measurement and scanning electronic microscopic (SEM) analysis also confirmed these findings. Contact angel measurements and atomic force microscopy (AFM) examinations and static absorption of collagen protein on the membrane surfaces revealed that EVA content up to 5 wt% lowered the hydrophobicity of the membrane. By EVA content above 10 wt%, due to the structural alteration on the membrane surface, the contact angel and the collagen absorption on the surface of membrane increased. The measurement of tensile strength showed that with increasing EVA content the mechanical properties of the membranes improved due to interactions of polar groups in EVA.