The oxidation behavior of a Zr-Nb-Cu alloy under high-temperature water conditions, with different dissolved hydrogen concentrations, was investigated using in situ Raman spectroscopy. The results were subsequently compared to those of ex situ TEM analyses. Upon decreasing the dissolved hydrogen concentration from 4.15 to 2.49. mg/kg at STP, the peak intensity of tetragonal phase oxide weakened, while that of monoclinic oxide strengthened due to the phase transformation. Ex situ analyses revealed that the Zr-Nb-Cu alloy was oxidized slowly as compared to the Zr-Nb-Sn alloy due to the number of β-Nb precipitates in the oxide.