Exported polysaccharides have many crucial functions in Gram-negative bacteria. In the ubiquitous Wzx/Wzy-dependent pathway, polysaccharide biosynthesis is initiated by a phosphoglycosyl transferase (PGTs), which catalyzes the transfer of a monosaccharide-1-P from nucleotide-sugar precursors to undecaprenyl phosphate (Und-P). Since precursors and Und-P are limited resources also required for the biosynthesis of other glycoconjugates, such as the essential peptidoglycan, the activity of these pathways is tightly regulated, commonly at the transcriptional level. In the Gram-negative bacterium Myxococcus xanthus, the exported exopolysaccharide (EPS) is important for crucial biological traits. EPS is synthesized and exported via the Wzx/Wzy-dependent EPS pathway. The PGT EpsZ initiates EPS biosynthesis by transferring galactose-1-P to Und-P. EPS biosynthesis is stimulated by the Dif chemosensory system through the phosphorylated single-domain response regulator EpsW. Importantly, the mechanism by which EpsW~P activates EPS biosynthesis is unknown. Here, we use global transcriptomic and proteomic analyses to demonstrate that EpsW regulates EPS biosynthesis at the post-translational level. MiniTurbo-based proximity labeling experiments strongly suggests that EpsW~P interacts directly with EpsZ. Previous structural characterization of the EpsZ-homolog WbaP in Salmonella enterica supports that it forms a functional homodimer, with dimerization involving a distinct cytoplasmic β-hairpin. Computational structural biology indicates that EpsZ lacks this β-hairpin, likely preventing it from dimerizing efficiently on its own. Remarkably, our computational analyses also support that EpsW promotes the formation of the active EpsZ dimer through direct interaction. Altogether, these findings support a model in which EpsW~P activates EPS biosynthesis at its initial step by facilitating the formation of the active conformation of the PGT EpsZ.