Production of an alkenoyl isocyanate of the formula: ##STR1## wherein R is a hydrogen atom or a lower alkyl group by reacting an acrylamide of the formula: ##STR2## wherein R is as defined above with an oxalyl halide of the formula(COX).sub.2wherein X is a halogen atom to give a reaction mixture comprising a haloalkanoyl isocyanate of the formula: ##STR3## wherein R and X are each as defined above with or without the alkenoyl isocyanate, recovering the haloalkanoyl isocyanate and, when present, the alkenoyl isocyanate separately from the reaction mixture and reacting the recovered haloalkanoyl isocyanate with a hydrogen halide-eliminating agent to give the alkenoyl isocyanate.