The peptide hormone glucagon is a fundamental metabolic regulator that is also being considered as a pharmocotherapeutic option for obesity, fatty/fibrotic liver, and type 2 diabetes. Despite this, we know very little of how glucagon exerts its pleiotropic metabolic actions. Given that the liver is a chief site of action, we conducted time-resolved phosphoproteomics using a perfused rat liver model to reveal glucagon signalling nodes. On pathway analysis of the thousands of phosphosites affected, we identified “vesicle transport” as a dominant signature with the vesicle trafficking protein SEC22 Homolog B (SEC22B) S137 phosphorylation being a top hit. Adeno-associated virus (AAV) mediated hepatocyte-specific loss- and gain-of-function experiments revealed that SEC22B was a key regulator of glucose, lipid and amino acid metabolism, with SEC22B-S137 phosphorylation only controlling distinct aspects such as serum lipid and amino acid metabolism. To explore potential mechanisms, we conducted immuno-precipitation (IP)-proteomics and found most enriched SEC22B binding proteins are involved in vesicle-mediated transport. Glucagon treatment significantly augmented SEC22B's association with lipid and amino acid metabolism pathways, with certain protein partners absent in the SEC22B-S137A mutant. In summary, here we demonstrate that phosphorylation of SEC22B is a hepatic signalling node modulating the metabolic actions of glucagon, and provide a rich knowledge resource for future investigations on the biology of glucagon action.