Folic acid (FA) is an essential vitamin; however, when exposed to ultraviolet (UV) radiation, it undergoes photodegradation to form fl uorescent products, specifically 6-carboxypterin and 6-formylpterin. These compounds belong to the class of pterins, which can act as endogenous photosensitizers and accumulate in the skin in certain pathologies. The interaction of these photoproducts with proteins, particularly serum albumin, the main transport protein of blood plasma and interstitial fl uid, determines their biodistribution and photosensitizing activity. In this study, the interaction of FA photodegradation products (FA-UV) with bovine serum albumin (BSA) has been studied using steady-state and time-resolved fl uorescence spectroscopy. It has been shown that the addition of BSA to the FA-UV solution leads to quenching of the fl uorescence of the photoproducts. Analysis of the Stern–Volmer plot revealed a deviation from linearity at high protein concentrations, indicating a complex quenching mechanism. The calculated quenching constant was KSV=2,8×104bМ−1, and the bimolecular quenching rate constant (kq =5,6×1012bМ−1s−1) signifi cantly exceeds the diff usion limit. This indicates the predominance of a static quenching mechanism due to complex formation. The binding constant was Kb = 6,5×104bМ−1, and the calculated number of binding sites (n≈0.97) indicates a 1:1 stoichiometry of the complex. These data demonstrate high binding of FA photodegradation products to BSA and can be used to further study the mechanisms of photoinduced damage to biomacromolecules.