Herein, we evaluate the photostability of pranoprofen (PP) tablets (NIFLAN® 75 mg), its powdered and suspended forms. PP is a member of the 2-arylpropionic acid family of NSAIDs. The content of the active compound was monitored by high-performance liquid chromatography (HPLC) using an ODS column with ultraviolet light (UV) detector. The residual amount of PP in the powder was 86.5%, which was comparable to that of in the suspension (85.4%) after UV irradiation for 24 hr. Further UV irradiation (total irradiation time of 7 days) resulted in the significant photodegradation of PP in the suspension (residual amount: 55.5%), compared to that of 1 day irradiation. However, the residual amount of PP in the powder was 78.6% after 7 days irradiation as the same to that of 1 day irradiation. To identify the chemical structure of five photoproducts generated from the UV-irradiated PP dosage forms, electrospray ionization liquid chromatography mass spectrometry (ESI-LC/MS/MS) analysis was performed. From these results, photodegradation of PP was observed through changing dosage forms. This is the first report evaluating the generation of PP photoproducts induced by the UV irradiation in the formulation.