Even if a superalloy has an optimal performance in dry oxidation and chemical corrosive environments, immunity to hydrogen embrittlement and water vapor effects in high-pressure hydrogen environments is not automatically guaranteed. Hydrogen embrittlement effects in superalloys have been observed over a broader temperature range, with significant embrittlement still evident at substantially higher temperatures compared to room temperature. Depending on the optimal operating pressure and temperature range, a careful choice must be made to ensure that the right specific alloys are employed in applications where there is a presence of hydrogen. HE susceptibility can vary significantly within each alloy system, and many of these superalloys have been identified as highly susceptible to hydrogen embrittlement based on the severity classification. All these issues are reviewed in the present chapter.