A method for treating a contaminated alkaline amino acid salt solution is provided. First, carbon dioxide is introduced into the amino acid salt solution, with the result that carbonate or carbonate salts is or are precipitated, these being filtered off. The remaining filtrate is then cooled, amino acid or amino acid salts being crystallized out and likewise being filtered off. The amino acid or amino acid salt is then dissolved again, with the result that a treated amino acid salt solution is recovered.