Crosslinkable alkyl-substituted poly(aryl ether ketone)s (PEKs) bearing a styryl group at both chain ends were synthesized by nucleophilic substitution reaction of 1,1’-(p-phenylenedioxy)bis[2-methyl-4-(4-fluorobenzoyl)benzene] with an excess aromatic diol in the presence of a base, followed by the reaction of the terminal phenol group with chloromethylstyrene. The aromatic diols used in this study were hydroquinone and resorcinol. The molecular weight of the polymer determined by GPC and H-1 NMR agreed with each other and close to the theoretical value calculated from the feed ratio. The polymer was soluble in N,N-dimethylacetamide and tetrahydrofuran, but insoluble in acetone and methanol. From DSC analysis, the polymer was thermally crosslinked around 220 degrees C. The addition of dicumyl peroxide as a radical generator in the polymer decreased the curing temperature. The cured polymer showed high thermal stability up to 420 degrees C under nitrogen.