Potassium Channel Tetramerization Domain containing 15 (Kctd15) has a role in regulating the neural crest (NC) domain in the embryo. Kctd15 inhibits NC induction by antagonizing Wnt signaling and by interaction with the transcription factor AP-2α activation domain blocking its activity. Here we demonstrate that Kctd15 is SUMOylated by SUMO1 and SUMO2/3. Kctd15 contains a classical SUMO interacting motif, ψKxE, at the C-terminal end, and variants of the motif within the molecule. Kctd15 SUMOylation occurs exclusively in the C-terminal motif. Inability to be SUMOylated did not affect Kctd15's subcellular localization, or its ability to repress AP-2 transcriptional activity and to inhibit NC formation in zebrafish embryos. In contrast, a fusion of Kctd15 and SUMO had little effectiveness in AP-2 inhibition and in blocking of NC formation. These data suggest that the non-SUMOylated form of Kctd15 functions in NC development.