Greenhouse gases Observing SATellite (GOSAT) is the operational satellite dedicated to atmospheric CO₂ observations. Assimilation of data provided by GOSAT is expected to yield reliable CO₂ fluxes in semi-arid regions because of frequent observations owing to clear skies. Here we estimated net CO₂ flux over semi-arid regions of the Southern Hemisphere using the GOSAT column averaged CO₂ (X_CO2) and surface CO₂ measurements. Assimilation of GOSAT X_CO2 indicated that semi-arid regions are integral components of recent terrestrial CO₂ uptake, accounting for 44% globally. Compared with estimates assimilated from surface measurements, estimates by GOSAT X_CO2 suggest a 50% reduction in the semi-arid CO₂ uptake, amounting to 1.1 Pg C yr⁻¹. Significant estimation differences occurred for South America and South Africa, where the GOSAT makes frequent measurements but where surface CO₂ measurements are limited. In comparison, the two estimates varied less in Australia, where more surface measurements are available. These results suggest that GOSAT X_CO2 is effective at regulating excess estimates of semi-arid CO₂ uptake in regions that are less constrained by surface CO₂ measurements. To promote understanding of climate change effects in semi-arid regions, it is important to continue monitoring trends in CO₂ uptake with GOSAT.