This study investigates the mechanical, flame-retarding, and creep-recovery proprieties of ethylene–propylene–diene monomer (EPDM) composites. The EPDM composites are filled with different contents of nano-Mg(OH) (NMH) or nano-Al(OH) (NATH). To examine the effect of contents of NMH (or NATH) and seawater immersion, mechanical tests are conducted and the limiting oxygen index (LOI) method was applied. Creep-recovery tests are then conducted to obtain the creep resistance property of EPDM composites with contents of NMH (or NATH). The microstructure of EPDM composites is investigated by using scanning electron microscopy (SEM). The results indicate that NMH (or NATH) can enhance the flame-retarding, creep resistance, and hardness properties, whereas tensile strength and elongation at break increase at first and then decrease with increasing content of NMH (or NATH). The Findley power law and the Weibull distribution function show good correspondence with the results of creep-recovery tests for EPDM composites. Furthermore, SEM results show good interfaces between nanoparticles and the matrix implying the mechanism of the above results.