Accurately estimating biogenic methane (CH4) and nitrous oxide (N2O) fluxes in terrestrial ecosystems is critical for resolving global budgets of these greenhouse gases (GHGs) and continuing to mitigate climate warming. Here, we assess contemporary biogenic CH4 and N2O budgets and probable climate-change-related impacts on CH4 and N2O emissions in terrestrial North America. Multi-approach estimations show that, during 1990–2010, biogenic CH4 emissions ranged from 0.159 to 0.502 petagrams of carbon dioxide (CO2) equivalents per year (Pg CO2eq yr–1, where 1 Pg = 1 × 1015 g) and N2O emissions ranged from 0.802 to 1.016 Pg CO2eq yr–1, which offset 47–166% of terrestrial CO2 sequestration (0.915–2.040 Pg CO2eq yr–1, as indicated elsewhere in this Special Issue). According to two future climate scenarios, CH4 and N2O emissions are projected to continue increasing by 137–151% and 157–227%, respectively, by the end of this century, as compared with levels during 2000–2010. Strategies to mitigate climate change must account for non-CO2 GHG emissions, given their substantial warming potentials.