A composite separator membrane (CSM) with an A/B/A type layered structure, composed of a microporous electrolyte-philic poly(vinylidene fluoride-co-hexafluoropropylene) (PVdF-HFP) gel layer (A) and a submicrometer porous polyethylene (PE) or a macroporous poly(ethylene terephthalate) (PET) non-woven matrix (B), is introduced in a dye-sensitized solar cell (DSSC). Commercially available PE and PET separator membranes (SMs) act as matrices that provide mechanical stability to the DSSC and permanent pore structures for facilitated ion transport. PVdF-HFP is used as a microporous gelator for improved interfacial contact between the solid SM and the electrodes. The PVdF-HFP gel impedes the charge recombination process between electron and I3 − at the TiO2/electrolyte interface, resulting in improved electron lifetimes. The DSSC assembled with the CSM exhibits high initial solar energy conversion efficiency (η, 6.1%) and stable η values over 1400 h, demonstrating good long term stability. The behaviors of the DSSC are attributed to the synergistic factors of the CSM, such as improved ion conductivity, electrolyte affinity, electrolyte retention capability, effective interfacial contact, and plausible passivation of the dyes. This study demonstrates a practical combination of short- and long-term DSSC performance through the introduction of the CSM.