This study investigates the effects of polymer concentration and solvent type on the pore size distribution (PSD) of the fabricated gas-liquid membrane contactors (MCs). Eighteen flat-sheet MCs are fabricated using polysulfone (PSf) and polyethersulfone (PES) polymers, with polymer concentration of 10%, 15%, and 20%. Dimethylformamide (DMF) and n-methyl-2-pyrrolidone (NMP) solvents are used to prepare the polymeric solutions. The role of polyvinylpyrrolidone (PVP) on the mean pore size of MCs is also studied. Scanning electron microscope (SEM) analysis is applied to visualize the pore system of the fabricated MCs. Image processing technique is used to obtain the PSD of the fabricated MCs using their SEM images. Experimental results indicate that increasing polymer concentration shifts the PSD of MCs toward smaller pores. Polymer concentration has negligible impact on the mean pore size of the NMP-based MCs. For the DMF-based MCs however, mean pore size significantly decreases by increasing polymer concentration. Also, NMP-based MCs have smaller pore size compared with the DMF-based MCs. Addition of PVP to the polymeric solutions lead to larger mean pores. This observation is very pronounced at low polymer concentration values.