Mechanochemistry is an effective method for the preparation of multicomponent crystal systems. In the present work, an alternative to the established liquid-assisted grinding (LAG) approach was proposed. Polymer-assisted grinding (POLAG) is demonstrated to provide a new class of catalysts for improving reaction rate and increasing product diversity during mechanochemical cocrystallization reactions. POLAG provides advantages comparable to the conventional liquid-assisted process, whilst eliminating the risk of unwanted solvate formation as well as enabling control of resulting particle size. It represents a new approach for the development of functional materials via mechanochemistry, and possibly opens new routes towards the understanding of the mechanisms and pathways of mechanochemical cocrystal formation and polymorphism.