The present invention provides, among other things, improved methods for purifying arylsulfatase A (ASA) protein produced recombinantly for enzyme replacement therapy. The present invention is, in part, based on the surprising discovery that recombinant ASA protein can be purified from unprocessed biological materials, such as, ASA-containing cell culture medium, using a process involving as few as four chromatography columns and only one step of post-chromatographic ultrafiltration/diafiltration.