Updated project metadata. During Caenorhabditis elegans oocyte meiosis, a multi-protein complex localised between homologous chromosomes, the ring complex (RC), promotes chromosome congression through the action of the chromokinesin KLP-19. While some RC components are known, the mechanism of RC assembly has remained obscure. A germline-specific screen identified KLP-19 as a SUMO substrate in vivo and we found that the SUMO E3 ligase GEI-17/PIAS is required for KLP-19 recruitment to the RC. Additionally, KLP-19 is efficiently sumoylated in vitro in a GEI-17-dependent manner. Further biochemical analysis showed that KLP-19 and GEI-17 are efficiently modified by SUMO and that GEI-17 and another RC component, the kinase BUB-1, can interact non-covalently with SUMO. While SUMO conjugation is required for RC assembly, we also provide evidence consistent with non-covalent SUMO interactions contributing to RC assembly in vivo. Our results highlight the importance of sumoylation and non-covalent SUMO interaction in regulating dynamic protein complex assembly during oocyte meiosis.