Sumoylation is a post‐translational modification system that covalently attaches the small ubiquitin‐related modifier (SUMO) to target proteins. Ubc9 is required as the E2‐type enzyme for SUMO‐1 conjugation to targets. Here, we show that Ubc9 interacts with the meiosis‐specific RecA homolog, Lim15/Dmc1 in the basidiomycete Coprinus cinereus (CcLim15), and mediates sumoylation of CcLim15 during meiosis. In vitro protein–protein interaction assays revealed that CcUbc9 interacts with CcLim15 and binds to the C‐terminus (amino acids 105–347) of CcLim15, which includes the ATPase domain. Immunocytochemistry demonstrates that CcUbc9 and CcLim15 colocalize in the nuclei from the leptotene stage to the early pachytene stage during meiotic prophase I. Coimmunoprecipitation experiments indicate that CcUbc9 interacts with CcLim15 in vivo during meiotic prophase I. Furthermore, we show that CcLim15 is a target protein of sumoylation both in vivo and in vitro, and identify the C‐terminus (amino acids 105–347) of CcLim15 as the site of sumoylation in vitro. These results suggest that sumoylation is a candidate modulator of meiotic recombination via interaction between Ubc9 and Lim15/Dmc1.