Shallow areas of lakes, known as littoral zones, emit disproportionately more methane than open water but are typically ignored in upscaled estimates of lake greenhouse gas emissions. Littoral zone coverage may be estimated through synthetic aperture radar (SAR) mapping of emergent aquatic vegetation, which only grows in water less than ~1.5 m deep. To assess the importance of littoral zones to landscape-scale methane emissions, we combine airborne SAR mapping with field measurements of littoral and open-water methane flux. First, we use Uninhabited Aerial Vehicle SAR (UAVSAR) data from the NASA Arctic-Boreal Vulnerability Experiment (ABoVE) to map littoral zones of 4,572 lakes across four Arctic-boreal study areas and find they comprise ~16% of lake area on average, exceeding previous estimates, and exhibiting strong regional differences (averaging 59 [50–68]%, 22 [20-25]%, 1.0 [0.8-1.2]%, and 7.0 [5.0-12]% for the Peace-Athabasca Delta, Yukon Flats, and northern and southern Canadian Shield areas, respectively). Next, we account for these vegetated areas through a simple upscaling exercise using representative, paired open water and littoral methane fluxes. We find that inclusion of littoral zones nearly doubles overall lake methane emissions, with an increase of 79 [68 – 94]% relative to estimates that do not differentiate lake zones. While littoral areas are proportionately greater in small lakes, this relationship is weak and varies regionally, underscoring the need for direct remote sensing measurements using vegetation or otherwise. Finally, Arctic-boreal lake methane upscaling estimates can be improved by more measurements from both littoral zones and pelagic open water.