The surface degradation of melt-crystallized poly(sebacic anhydride) (PSA) has been visualized in situ in an aqueous environment using atomic force microscopy. The morphological changes accompanying degradation may be interpreted in terms of the preferential erosion of amorphous material revealing spherulitic crystalline features. The kinetics of polymer degradation were found to be pH dependent as anticipated and also dependent on the method of sample preparation, which influenced surface crystallinity. The future exploitation of in situ atomic force microscopy for the study of polymer degradation promises to provide a unique insight into the erosion process and enhance the current understanding of the relationship between polymer microstructure and erosion kinetics.