Regeneration of an ammoxidation catalyst which is exhausted as a result of prolonged exposure to ammoxidation conditions, containing oxides of Mo, Bi, P, Fe, Co, Ni and possibly an alkali metal, particularly K, on a granular support, particularly silica, by means of a method including:the impregnation of the granules of spent catalyst with an aqueous molybdic acid solution, or with an aqueous solution of partially or totally salified molybdic acid in the form of the ammonium salt, with a volume of impregnation solution less than the total pore volume of the catalyst subjected to regeneration;the drying of the impregnated granules at a temperature of from 100.degree. to 200.degree. C.;the calcining of the dried granules at a temperature of from 250.degree. to 450.degree. C., solely when the impregnation is with an aqueous solution of partially or totally salified molybdic acid.Under ammoxidation conditions, the catalyst regenerated in this manner displays characteristics of activity, selectivity and of mechanical strength similar to those of the fresh catalyst.