In the context of climate change and waste management, transforming locally available waste into valuable resources for construction is essential. The main objective of this study is to transform low-value crustacean waste (CW) into an accelerating admixture for cementitious systems. This study investigates the impact of ultrasonication on heat-treated, ground CW particles. The impact of incorporating 10% CW, ground using roller-mill and high-shear grinders, without and with ultrasonication, was evaluated in terms of slump flow, compressive strength, and heat of hydration. The results showed that undispersed CW reduced compressive strength by about 10%, whereas ultrasonicated CW led to a 30% increase in both early and later-age strengths. The system with 10% ultrasonicated CW exhibited accelerated hydration kinetics, including a 4% increase in the C3S hydration and a 12% reduction in the time to reach maximum heat release. This was attributed to filler and nucleation effects. These findings highlight the importance of dispersing alternative fine materials within cementitious systems to improve the compatibility of these materials in developing sustainable cement-based systems.