Aluminum methacrylate (AIMAA) was in situ prepared in EPDM matrix through neutralization of aluminum hydroxide and methacrylic acid during mixing. The resulting compound was vulcanizated with peroxide. Mechanical properties of EPDM/Al-MAA vulcanizates without any traditional reinforcing fillers were measured showing that AIMAA has effective reinforcement on EPDM. The tensile strength of the vulcanizate can reach 28 MPa, while its elongation at break remains over 400%. To act both as a crosslinking agent to EPDM and as an initiating agent for polymerization of AIMAA, dicumyl peroxide has an optimum amount of 3 phr. Crosslink densities of EPDM/AIMAA vulcanizates were measured. The reinforcing effects of the in situ prepared AIMAA on several elastomers were also investigated.