Swamps are forested wetlands that account for a large portion of the wetland area of Canada and up to 87% of total wetland spatial extent remaining in southern Ontario. Trees in swamps store large amounts of carbon (C) and potentially significant amounts of carbon in soils that range from mineral to meters-deep peat. Despite their prevalence and potential as natural climate solutions, swamps are under-represented in carbon accounting and modeling due to difficult access and unclear classification relative to other wetland types. Currently, most data on swamps comes from subtropical and tropical sites rather than temperate and boreal regions found in Canada. Four swamps in southern Ontario, Canada were selected to build a C budget that includes net exchange of carbon dioxide (CO2) and methane (CH4) between soil, trees, and the atmosphere, and determine the amount of C stored in understory vegetation, trees, and debris, and in the soil itself. Carbon stocks held in trees ranged from 14 - 21 kg C m-2, woody debris 0.4 - 1.4 kg C m-2, and with mean peat depths of 38 - 142 cm, soil C stocks held 18 - 86 kg C m-2. Methane release was relatively low at 0 – 6.5 g C m-2 yr-1 from soil and 0 – 1.5 g m-2 yr-1 from tree stems while CO2 soil fluxes were 1045 – 1380 g m-2 yr-1. Annual net primary productivity at all sites exceeded losses by flux, making all four sites net sinks of C.