Studies were undertaken to investigate the effects of ultraviolet (UV) irradiation on the gel strength, color, thermal properties, protein molecular masses, and functional groups of commercially available fish gelatin samples. Commercially available tilapia skin gelatin powder was used as the raw material to investigate the functional properties of fish skin gelatin powder treated with UV irradiation for different durations (0–6 h). The functional properties of fish gelatin and the optimum irradiation treatment conditions were determined through gel strength testing, color characterization, differential scanning calorimetry, sodium dodecyl sulfate polyacrylamide gel electrophoresis, Fourier transform infrared (FTIR) spectroscopy, and Raman spectroscopy. UV irradiation treatment increased gel strength and thermal stability, and significantly degraded the macromolecules. FTIR and Raman spectroscopy data indicated that UV irradiation treatment did not significantly change the molecular structure of fish gelatin powder, but these methods could discriminate the molecular structure of gelatin from various sources. Irradiation for 2 h yielded the highest gel strength and melting peak temperature, and the lowest chromatic aberration.