Increasing drought frequency can jeopardize the restoration of the CO₂ sink function in degraded peatlands. We explored the effect of the summer drought in 2018 on vegetation development and CO₂ exchange in a rewetted fen. Drought triggered a rapid spread of new vegetation whose CO₂ assimilation could partially outweigh the drought-related rise in respiratory CO₂ loss. Our study shows important regulatory mechanisms of a rewetted fen to maintain its net CO₂ sink function even in a very dry year.