The effects of UV-C radiation, modified atmosphere packaging (MAP) and their combination on rainbow trout (Oncorhynchus mykiss) fillets quality were examined during a period of 22 days. The samples were submitted to five packaging conditions: (AP) aerobic packaging; (VP) vacuum packaging; (VP + UV-C) vacuum packaging + UV-C radiation; (MAP) modified atmosphere packaging (80% CO2/20% N2) and (MAP + UV-C) modified atmosphere packaging + UV-C radiation (80% CO2/20% N2; 106.32 mJ/cm2) and storaged at 4 °C. The samples were analyzed daily for microbiological (mesophilic, psychrotrophic and Enterobacteriaceae counts) and chemical (pH, TMA-N, TBV-N, lipid oxidation, ammonia and biogenic amines) parameters. Overall, UV-C radiation promoted lag phase formation in mesophilic and psychrotrophic groups. Mesophilic and psychrotrophic groups presented significant lower (P < 0.05) growth rate and colony forming units in the stationary phase in the samples submitted to MAP. MAP significantly reduced (P < 0.05) total mesophilic count and MAP + UV-C total mesophilic and psychrotrophic counts. Values of pH decreased at all packaging conditions except in the case of aerobic packaging. TBARS value increased faster in samples subject to MAP and MAP + UV-C whereas TMA-N, TVB-N and ammonia values increased slowly. Lower production of putrescine and cadaverine was observed in MAP and VP samples. MAP reduced total production of ammonia, TVB-N and putrescine, whereas MAP + UV-C reduced total production of TVB-N and cadaverine during entire the storage time. Results of the current study suggest that MAP retarded microbial growth and delayed chemical changes enhancing the shelf life of rainbow trout fillets at least twice.