In a process for preparing polyarylene sulfides by reacting a dihalo-aromatic compound with a sulfur source in an organic amide solvent in the presence of an alkali metal salt of carboxylic acid as a polymerization aid or assistant, a specific class of carboxylic acids are employed for preparing the alkali metal salt polymerization aid. The specific carboxylic acids are of the general formula: R(COOH).sub.n (wherein R is a C.sub.1 -C.sub.20 organic radical and n is an integer not less than 1) and have a solubility of not less than 3 g/100 ml in ethanol at 20.degree. C. Use of such a carboxylic acid in the process permits the recovery thereof from the polymerization mixture to be effected with significantly improved efficiency.