Parks Canada collaborates with partners to manage a growing system of national marine conservation areas (NMCAs) and national marine conservation area reserves (NMCARs). These ecologically and culturally varied marine protected areas are established to represent the rich diversity of Canada’s oceans and Great Lakes. They support a broad range of uses within specific zones, including recreation, tourism, fishing, shipping, and Indigenous rights-based activities. Long-term monitoring is a critical tool for tracking changes in marine ecosystems, developing strategies to protect and conserve ecological and cultural values, responding to environmental threats, and ensuring ecologically sustainable use of marine resources that provide long-term societal benefits. Monitoring involves working closely with Indigenous partners, federal departments, provincial/territorial governments, coastal communities, and others (e.g., fishing and tourism sectors, non-governmental organizations, academia). As part of larger seascapes, NMCAs are managed using an ecosystem approach, which requires information on the state of marine biodiversity, threats, and pressures on marine ecosystems, including levels or impacts of marine uses. Each NMCA monitors a site-specific suite of indicators covering these key characteristics that are then integrated to inform decision-making. The monitoring framework is intended to enable a comprehensive, nationally consistent approach to monitoring and reporting while adapting to local needs and governance. Successes, challenges, and lessons learned through the implementation of the framework are highlighted through place-based examples.