Modulation of protein activities by SUMO-dependent modification has emerged as a key feature of cellular regulation. Evidence of the localization of different enzymes of the sumoylation-desumoylation cycle at nuclear pore complexes (NPCs), and of its biological relevance, has steadily accumulated over the past ten years. Recent findings indicate that, beyond nucleocytoplasmic transport, sumoylation processes underpin newly emerging, and initially unexpected, roles for NPCs in a broad array of biological functions. These include cell division, DNA repair, DNA replication and mRNA quality control. Most of these functions were initially discovered through genetic studies in budding yeast, but the localization of SUMO-proteases at NPCs in higher eukaryotes suggests that at least some of these mechanisms might have been conserved during evolution.