When user needs do not align with system designers’ visions, new technology implementation becomes a complex process as users appropriate the new technology to meet their needs. Prior studies recognize this complexity, but focus on the complex implementation of simple systems in which user groups are well defined and the IT artifact is the primary change. We extend the research lens by examining the implementation of the Brazilian correspondent banking system, a complex system involving multiple actors, system elements, and settings intended to address the social problem of financial exclusion. Our case study comparison of two settings—retail stores and post offices—reveals that actors’ appropriations extended beyond the IT artifact to include technical, role, usage, social, and policy appropriations. The intended users (poor clients in remote and underserved areas) barely interacted with the IT artifact or other system elements; instead, they relied upon remote bankers (correspondents) to appropriate the system on their behalf. Because rewards, incentives, and constraints differed by setting, correspondents’ appropriations differed by setting. We call the resulting mix of appropriations across multiple elements by multiple actors in multiple settings multiplex appropriation. Complex societal challenges often involve multiple users in multiple settings with varied needs and few technology skills; thus, designing systems to meet user requirements may prove impossible. Instead, allowing multiplex appropriation might foster system success because, rather than forcing a global alignment among system elements or trying to ascertain multiple user needs, it allows for multiple local alignments of system elements that fit local settings.