<p>Crystallization is a cornerstone of pharmaceutical manufacturing, fundamentally influencing the physicochemical properties, bioavailability, and therapeutic efficacy of active pharmaceutical ingredients (APIs). Traditional crystallization processes, while critical, face significant challenges, particularly with poorly soluble drugs and the control of polymorphic forms, which are essential for ensuring drug stability and performance. Deep Eutectic Solvents (DES) have emerged as a novel class of solvents offering unique advantages in pharmaceutical crystallization, addressing these challenges through their tunable properties and eco-friendly nature. This review provides a comprehensive examination of recent advancements in the use of DES for pharmaceutical crystallization. It explores the fundamental mechanisms by which DES modulate crystallization processes, including their impact on drug solubility, polymorphism, and crystal purity. The review highlights the versatility of DES in enhancing the crystallization of poorly soluble drugs and controlling polymorphic outcomes, thereby improving the development and manufacturing of high-quality pharmaceuticals. Additionally, the environmental and economic benefits of DES are discussed, positioning them as a sustainable alternative to conventional solvents.</p>