This study explores the transformative impact of substituting cement with raw marble powder (RMP) and calcined marble powder (CMP) at varying levels (0%, 5%, 10%, 15%, 20%, and 25%) on the physical and mechanical properties of cement-based composites. Additionally, the influence of two different mixing waters—tap water (TW) and magnetized water (MW)—was assessed to determine their combined effects on the composite performance. The evaluation encompassed fresh properties (initial and final setting times, and consistency) and hardened properties (flexural strength (ffs), compressive strength (fcs), ultrasonic pulse velocity (UPV), water absorption, porosity, and unit weight) of the composites. The results reveal that CMP-substituted composites significantly outperformed RMP-based counterparts across all indices. Notably, CMP-substituted mortars produced with TW showed a 10.8% to 15.8% increase in 28-day fcs values compared to RMP-substituted mortars, while those prepared with MW exhibited 7.8% to 10.9% higher fcs values than TW-prepared samples. A microstructural analysis via SEM indicated that CMP enhances hydration and microstructure densification, resulting in improved mechanical performance and durability. Overall, the combination of CMP and MW demonstrated a superior potential for producing eco-friendly, high-performance cementitious composites, supporting sustainable construction practices through significant material savings and environmental benefits.