Alloy 725 (UNS N07725) is a Cr- and Mo-rich precipitation-hardened nickel alloy known for its superior mechanical and corrosion properties. Although the alloy has been widely used for subsea oil and gas production, reported failures in H-bearing environments had demonstrated their susceptibility to hydrogen embrittlement. These high-profile incidents have led to extensive research to elucidate the failure mechanism and develop methods to reduce risks. However, the microstructural features that made only specific batches of Alloy 725 susceptible to hydrogen embrittlement have yet to be agreed upon by the scientific community. Herein, our results showed that a failed commercial batch presented extensive intergranular precipitation dominated by F phase, i.e., a recently discovered nano-thin and σ-related topologically close-packed phase. Because of its thickness, regular metallographic procedures could not detect the intergranular precipitate. The abundant precipitation of F phase at grain boundaries increased cracking susceptibility since it offered a low-energy path for crack opening by matrix-precipitate interfacial decohesion. The correlation of an Alloy 725 microstructure with hydrogen embrittlement field failure evidenced the importance of minimizing F phase formation. Additionally, it suggested new approaches to mitigate the risk for further hydrogen embrittlement failures of Cr- and Mo-rich nickel alloys.