Campylobacter jejuni is the leading cause of acute bacterial diarrhea worldwide and is implicated in development of Guillain-Barré syndrome. Two major surface features, the outer membrane lipooligosaccharide and flagella, are highly variable and are often targets for modification. Presumably, these modifications provide a competitive advantage to the bacterium. In this work, we identify a gene encoding a phosphoethanolamine (pEtN) transferase (Cj0256) that serves a dual role in modifying not only the lipooligosaccharide lipid anchor lipid A with pEtN, but also the flagellar rod protein FlgG. Generation of a mutant in C. jejuni 81-176 by interruption of cj0256 resulted in the absence of pEtN modifications on lipid A as well as FlgG. The cj0256 mutant showed a 20-fold increase in sensitivity to the cationic antimicrobial peptide, polymyxin B, as well as a decrease in motility. Transmission EM of the cj0256 mutant revealed a population (approximately 95%) lacking flagella, indicating that, without pEtN modification of FlgG, flagella production is hindered. Most intriguing, this research identifies a pEtN transferase showing preference for two periplasmic substrates linking membrane biogenesis and flagellar assembly. Cj0256 is a member of a large family of mostly uncharacterized proteins that may play a larger role in the decoration of bacterial surface structures.