Diethyl maleate is widely used as a reactive diluent and crosslinking agent in polymer chemistry. It helps reduce the viscosity of resins during processing, making them easier to handle in coatings, adhesives, and composite formulations. Due to its electron-deficient double bond, it participates in Michael addition reactions, making it valuable in organic synthesis for building complex molecules.

It is also employed in the production of copolymers with tailored properties such as flexibility, adhesion, and thermal stability. In industrial applications, diethyl maleate improves the performance of lubricants and stabilizers in plastics. Additionally, it serves as an intermediate in the synthesis of pharmaceuticals and agrochemicals, where its ester groups and unsaturated backbone allow for further functionalization.