Imidazolium-type basic ionic liquids (BILs), including 1-butyl-3-methyl imidazolium hydroxide ([Bmim][OH]), 1-butyl-3-methyl imidazolium phosphate ([Bmim][PO₄]), 1-butyl-3-methyl imidazolium carbonate ([Bmim][CO₃]), and 1-butyl-3-methyl imidazolium bicarbonate ([Bmim][HCO₃]), coordinated by iron chloride (FeCl₃·6H₂O), were used as both the ligand and catalyst in activators generated by the electron transfer ATRP (AGET ATRP) of methyl methacrylate (MMA) in bulk and solution, without the use of traditional ligands (such as 2,2-bipyridine, tetrabutylammonium bromide, and tetra-n-butylphosphonium bromide). Catalytic amounts of BILs could enhance the initiator efficiency (0.87–0.91) and the polymerization rate, and produce PMMA with controllable molecular weights and narrow molecular weight distributions (M_w/M_n = 1.20–1.40). The nature of the controlled/“living” free radical polymerization in the presence of BILs was confirmed by chain-extension experiments. The ready solubility and availability of BILs enable them to be applied as a new type of ligand and catalyst in iron-mediated AGET ATRP.