A polybenzoxazine bearing allyl group in the side chain was synthesized by the ring-opening polymerization of N-allyl-benzoxazine and was crosslinked by the two different processes, (1) thermally induced oligomerization of the allyl side chains and (2) radical addition of dithiol (thiol-ene reaction) to the allyl side chains. The former process was promoted by adding 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane as a radical source, leading to the improved yield of the networked polymer isolated as acetone-insoluble fraction. The thiol-ene reaction with using 1,6-hexanedithiol was also an efficient method for crosslinking the polybenzoxazine. (c) 2013 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013, 51, 2035-2039