This article analyzes the reign of King Tu Duc, the longest-serving monarch in the Nguyen Dynasty (1847–1883), focusing particularly on his seminal work, Khiêm Cung ký. The study draws upon diverse sources, including royal decrees, archival materials from the Quoc su quan trieu Nguyen (National Historical Bureau of Nguyen Dynasty), as well as scholarly contributions from both Vietnamese and international academics. Notably, it incorporates a complete translation of Khiêm Cung ký by Phan Hua Thuy, published on the Hồn Việt website. The research identifies Khiêm Cung ký as a significant landmark within the annals of traditional Vietnamese literature, serving as both a reflective assessment of King Tu Duc’s life and a candid acknowledgment of the limitations inherent within the dynasty. Despite Tu Duc’s discerning recognition of his own fallibility, the inscription also exposes his adherence to conservative ideologies and the inherent contradictions within his governance. His reign was characterized by multifaceted challenges, including socio-political upheavals, external aggressions, internal familial discord pertaining to succession, and the monarch’s personal health afflictions, notably his failure to produce a legitimate heir. Furthermore, the inscription not only holds intrinsic historical value but also offers invaluable insights and lessons for posterity. It serves as a cautionary tale, illustrating the complexities and vicissitudes of dynastic rule, while also shedding light on the topics of leadership, governance, and self-reflection. The study contributes to a deeper understanding of Vietnam’s historical trajectory and provides a foundation for future research in this field.