Langle-Flores, A.; Ocelík, P., and Pérez-Maqueo, O., 2017. The role of social networks in the sustainability transformation of Cabo Pulmo: A multiplex perspective. In: Martinez, M.L.; Taramelli, A., and Silva, R. (eds.), Coastal Resilience: Exploring the Many Challenges from Different Viewpoints. Journal of Coastal Research, Special Issue No. 77, pp. 134–142. Coconut Creek (Florida), ISSN 0749-0208.Coastal tourism is often caught in a crossfire between economic benefits, ecological impacts and social tensions. Development of large-scale resorts can reduce the provision of certain ecosystem services and threat local people's livelihoods. Social networks might influence the transitions of governance systems into new adaptive models. We focus on the role of multiplex networks in the process of sustainability transformation by examining social networks that protected a marine reserve against the construction of a large scale development. The multiplex network exhibited a structure with five blocks: “scale-crossing brokers”, “visible leaders”, “ecosystem managers”, “visionaries” and “public sector”. This last block was structurally isolated from the rest of organizations. Multiplex networks facilitated the coordinated mobilization of information and resources across spatial scales. “Scale-crossing brokers” with the aid of “visible leaders” propelled up the local conflict toward national and global arenas, affecting the decision of Mexico's federal government to annul large scale resort's construction. Understanding the social processes that enable adaptive governance systems is crucial for sustainability transformations and resilience of coastal ecosystems.