Caffeine belongs to a group of purine alkaloids. Complexes that albumin build with drug molecules represent a depot from which the drug is gradually released. Haloperidol (HPD) belongs to the group of atypical antipsyhotics and it is binding to human serum albumin (HSA) more than 90 %. The aim of this study was to determine the effect of caffeine on the binding of haloperidol to HSA. Reviewing the results will determine whether and how the caffeine affects the binding of haloperidol to HSA. Binding of haloperidol and caffeine was investigated by fluorescence spectroscopy. All fluorescent spectra were recorded in the range of 300 to 550 nm at a wavelength of excitation of 295 nm on two temperatures (303 and 310 K). Fluorescence spectroscopic data showed that the fluorescence quenching of HSA resulted from the formation of the HPD-HSA-Caffeine complex. Spectroscopic analyses on different therapeutic agents indicate that the mechanics of quenching human serum albumin with haloperidol and caffeine are a static process. Estimated constants (Ksv, Ka) and binding sites (n), between haloperidol, caffeine and human serum albumin, are Ksv 2.71 × 10³ l/mol, Ka = 9.27 × 10³ l/mol at a temperature of 303K, and Ksv 1.83 × 10³ l/mol, Ka = 9.33 × 10³ l/mol at a temperature of 310K. The number of operating points is 1. Caffeine affects the binding of haloperidol to HSA. It leads to a greater stabilization of the HSA-HPD complex. These results indicate the possible impact and significance of the interaction of medicinal products.