There is provided a method for producing a carboxyl group-containing polymer composition that is excellent in all of the following: dispersibility in water or the like immediately after the preparation, storage stability, and the transparency of a neutral viscous solution thereof. A method for producing a carboxyl group-containing polymer composition, the carboxyl group-containing polymer composition comprising a carboxyl group-containing polymer (A) that is a copolymer of monomers comprising an α,β-unsaturated carboxylic acid (a-1) and a compound (a-2) having at least two ethylenically unsaturated groups per molecule; and a nonionic surfactant (B), the method comprising the step of copolymerizing the monomers, wherein in the step, the nonionic surfactant (B) is added into the system when the polymerization degree of the α,β-unsaturated carboxylic acid (a-1) has reached 70 to 100%.