This study employs Harmonic Serialism (HS) to revisit phonologically conditioned suppletive allomorphy (PCSA) in Korean nominal suffixes. Multiple inputs and allomorph ordering has been suggested due to cases of allomorphy that phonological information alone has trouble accounting for. PCSA in Korean nominal suffixes provides another example, calling for both phonological and morpho-syntactic information. In particular, a special apparatus like Default (Bye 2007) or Priority (Mascaró 2007) is in need to select a marked or non-TETU allomorph as a preferred one over its unmarked or TETU counterpart. Drawing on previous works, the present study compares the analysis in classic OT with that in HS. It is shown here that the basic tenets of HS, gradualness and harmonic improvement, account for the phenomenon in a simple and natural way.