The trafficking regulator of GLUT4-1 (TRARG1) protein positively regulates insulin-stimulated GLUT4 trafficking. Here we identify post-translational modifications on TRARG1 and identify that GSK3 is the upstream kinase responsible for TRARG1 phosphorylation at Serines 72, 76, and 80. We employ affinity enrichment mass spectrometry to identify protein interactions regulated by TRARG1 phosphorylation.