The rapid development of hydrogen-based mineral transformation technologies has generated increasing amounts of iron ore tailings with distinct physicochemical characteristics, creating new challenges for resource utilization. This study investigates the mineralogical characteristics and cementitious utilization potential of hydrogen-based mineral phase transformation iron ore tailings (HMPT-IOTs). The effects of HMPT-IOTs incorporation on the hydration behavior, mechanical performance, and microstructural evolution of cement-based materials were systematically evaluated. The results indicate that HMPT-IOTs mainly consist of Fe-containing phases and silicate minerals, and their heterogeneous particle characteristics provide potential reactive sites in cementitious systems. The incorporation of HMPT-IOTs influences hydration kinetics by modifying early-age reaction processes. Among the investigated mixtures, the replacement of cement with 10 wt% HMPT-IOTs exhibited the most favorable performance, achieving a balanced improvement in mechanical properties and tailings utilization efficiency. Microstructural analysis revealed that HMPT-IOTs participate in hydration reactions and promote the formation of additional hydration products, contributing to matrix densification. This study demonstrates a feasible pathway for the high-value utilization of hydrogen-based iron ore tailings and provides insights into the physicochemical mechanisms governing their application in sustainable cementitious materials.