Envelope integrity is essential for diderm bacteria. The envelope is composed of an inner membrane (IM) and an outer membrane (OM), which are separated by a periplasmic space. Several pathways have been recently identified that facilitate the transport of phospholipids between the two membranes in Escherichia coli, including the maintenance of OM lipid asymmetry (Mla) and paraquat inducible (Pqi) systems. In this study, we report the identification and characterisation of a complex named Mpc in the intracellular pathogen Brucella abortus. Mpc is conserved in numerous species of Hyphomicrobiales and exhibits homology to both the Mla and Pqi systems. Mpc is essential for bacterial growth under conditions of envelope stress and for survival within macrophages during the early stages of infection. Analyses of protein-protein interactions and structural predictions indicate that the Mpc complex forms a stable entity that spans the entire periplasmic space. The absence of this system results in an altered lipid composition of the OM vesicles, which supports the hypothesis that it plays a role in the trafficking of lipids between the IM and OM. The discovery of a novel lipid trafficking system enhances the diversity and complexity of known lipid trafficking systems within diderm bacteria.