Low-pressure plasma treatments in a 13.56 MHz RF glow discharge of Hydrogen (H2)/Oxygen (O2) gas mixture were used to introduce polar functional groups onto microporous polypropylene (PP) membrane surfaces to improve the hydrophilicity and surface modification. The change in hydrophilicity and surface free energy was monitored by static contact angle measurement. Significant increased surface energy of polypropylene membranes from the H2/O2 mixture gas plasma treatments was observed. The PP membrane surfaces became highly hydrophilic when exposed for only 5 s to the H2/O2 mixture gas plasma. Optical emission spectroscopy (OES) was used to examine the various chemical species of low pressure plasma processing. The chemical structure and surface morphological changes on the membrane surface were characterized by X-ray photoelectron spectroscopy (XPS) and confocal laser scanning microscopy (CLSM). XPS analysis showed significantly higher surface concentrations of oxygen functional groups for H2/O2 mixture gas plasma-modified PP membrane surfaces than the originally unmodified PP membrane surfaces. The experimental results revealed low pressure H2/O2 plasma processing is an effective method to improve the surface hydrophilicity of microporous PP membranes. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012