Molybdenum bismuth selenide (MoBi2Se5) has been proved to be a promising material for photoelectrochemical solar cell application. As MoBi2Se5 thin films are more corrosion resistant than bismuth (III) selenide (Bi2Se3) thin films, MoBi2Se5 can also be used as a buffer layer due to its distinctive optostructural properties. In this study, the authors synthesized surfactant-assisted nanostructured MoBi2Se5 thin films by using a cost-effective chemical route – namely, the arrested precipitation technique. The synthesized thin films were analyzed for optostructural, surface morphological, compositional and photovoltaic applications using the X-ray diffraction (XRD) technique, ultraviolet–visible spectroscopy, scanning electron microscopy and energy-dispersive X-ray spectroscopy, and their photoelectrochemical solar cell performance was checked. The nanocrystalline nature of MoBi2Se5 thin films was confirmed from the XRD patterns. An increment in the optical bandgap energy was observed with surfactant mediation. The surface morphology of MoBi2Se5 changed from spherical to spongy-ball-like nanofibrous surface morphology after surfactant assistance. Furthermore, both the as-synthesized and surfactant-assisted MoBi2Se5 thin films showed photoelectrochemical solar cell applicability.