Significance The outer membrane of Gram-negative bacteria presents a selectively permeable barrier to the environment and is the first line of defense against antibiotics and other antimicrobial agents. Maintenance of the outer membrane relies on lipoproteins delivered by the LolABCDE system, making the Lol proteins attractive targets for the development of new antimicrobial compounds. During trafficking, lipoproteins are extracted from the cytoplasmic membrane by the LolCDE complex, transported across the periplasm by LolA, and integrated into the outer membrane by LolB. Here, we describe structural features underpinning the interaction between LolA and LolCDE. The structure of LolA bound to the periplasmic domain of LolC provides an arresting molecular snapshot of a key intermediate in the bacterial lipoprotein trafficking pathway.