A readily crystallizable arylenesulfide resin composition is produced by adding, to 100 parts by weight of an arylenesulfide polymer, 0.01 to 10.0 parts of an organic acid or organic acid anhydride having a high boiling or melting point such as 2,6-naphthalene dicarboxylic acid, and then heating the mixture to a temperature not lower than the melting point of the polymer. The resulting resin composition is characterized in that its crystallization from its glass state and molten state is very rapid, in that it forms very fine spherulite structures, and in that it has a high degree of crystallization, a very crystallizable character, and other desirable characteristics.