Intracellular transport occurs through two general types of carrier, either vesicles^, or tubules^,. Coat proteins act as the core machinery that initiates vesicle formation^,, but the counterpart that initiates tubule formation has been unclear. Here, we find that the coat protein I (COPI) complex initially drives the formation of Golgi buds. Subsequently, a set of opposing lipid enzymatic activities determines whether these buds become vesicles or tubules. Lysophosphatidic acid acyltransferase-γ (LPAATγ) promotes COPI vesicle fission for retrograde vesicular transport. In contrast, cytosolic phospholipase A2-α (cPLA2α) inhibits this fission event to induce COPI tubules, which act in anterograde intra-Golgi transport and Golgi ribbon formation. These findings not only advance a molecular understanding of how COPI vesicle fission is achieved, but also provide insight into how COPI acts in intra-Golgi transport and reveal an unexpected mechanistic relationship between vesicular and tubular transport.