Process for carboxy-alkylation, particularly carboxymethylation, of branched alcohols includes the reaction of isoalcohols with potassium-t-butoxide or sodium-t-butoxide and with salt of halogenated alkanoic acid in the presence of the isoalcohol (starting alcohol) as the solvent. Produced are isoalcohol carboxy-alkylates (preferably, carboxymethylates) in excellent yields and purity.