In the Northern Shelf Bioregion (NSB) along the North Pacific coast of British Columbia (BC), the Governments of Canada, BC, and 16 First Nations are developing a network of Marine Protected Areas (MPAs). MPA networks are designed and implemented globally to meet a range of biodiversity conservation and sustainable use goals and typically allow a range of human activities. Thus, possible cumulative impacts must be considered when designing effective MPA networks to ensure adequate representation of ecological features the networks are designed to protect. Here we present an approach for incorporating potential cumulative impacts into MPA network design.  First, we ascertain the spatial overlap of ecological features within the boundaries of existing MPAs and proposed new sites in the NSB. Second, we determine the potential impact of human activities within each site based on activity restrictions identified in the management plans of existing sites and proposed restrictions for new sites. An adjustment factor, developed from a meta-analysis on protected area effectiveness, is applied to each ecological feature based on the anticipated cumulative effects of human activities impacting the feature within each site. Comparing the proportion of each feature within the preliminary network to the values adjusted considering cumulative effects gives an indication of how human activities may influence the network’s effectiveness for each feature. While additional research on the ecological effectiveness of varying MPA protection levels is warranted, our case study highlights the utility of incorporating possible cumulative impacts during the design of terrestrial or marine protected area networks.