The iron-catalyzed methylation of arylboron compounds has been developed for the first time using iodomethane (CH3I) as the electrophile. In the presence of catalytic amounts of an iron-bisphosphine complex and MgBr2, Suzuki-Miyaura-type cross-coupling reactions of CH3I with various arylboron compounds proceed smoothly under mild conditions to afford the corresponding methylated aromatic compounds in good yields.