Abstract Shape‐morphing of thermosets is challenging due to their permanently cross‐linked polymer network structure. Here, a magnetothermal shape‐morphing strategy is proposed for complex thermoset structures via reshaping, assembly, and shape memory. The thermoset composite is fabricated by adding magnetic nanoparticles into dynamically cross‐linked thermoset resin, which imparts magnetothermal effect and reprocessability under an alternating magnetic field. Epoxy composites are prepared with various weight fractions of Fe 3 O 4 nanoparticles, and their magnetothermal and thermomechanical properties are studied. For a composite with 15 wt% Fe 3 O 4 nanoparticles, the glass transition temperature T g is 62 °C, and the topology freezing transition temperature T v is 175 °C. An alternating magnetic field with a working power of 2000 W can generate a temperature of 156 °C, enabling bond exchange reactions and stress relaxation in the dynamically cross‐linked epoxy resin. Magnetothermal reshaping and bonding facilitate the assembly of complex‐shaped structures from simple units, while magnetothermal shape memory provides rapid actuation deformation responses within 60 s. Various examples of magnetothermal shape‐morphing of complex thermoset structures, including grasper, origami, and octopus‐inspired functional structures, are demonstrated. The results indicate that the present shape‐morphing strategy provides advantages such as remote control, high efficiency, flexible design, and straightforward structural fabrication.