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Abstract: The impact of climate change (i.e. warming and changes in precipitation patterns) on carbon (C) sequestration in the continental steppe is currently disputed and uncertain. We conducted a six-year field experiment in the temperate grassland ecosystem in Inner Mongolia, China. We found that C storage in the 0–30cm soil layer significantly decreased by 129.3gCm−2 under warming (W) but significantly increased by 145.9gCm−2 with increased precipitation (P), with no apparent interaction of W×P. The effects of W and P on soil C sequestration varied in different soil fractions (labile vs. recalcitrant soil organic matter) and layers (topsoil vs. subsoil), which complicated the prediction of the short- and long-term effects of soil C sequestration in climate change scenarios. Furthermore, C:nitrogen (N) ratios in soils with increasing C and N were asynchronous under W, P, and W+P treatments, suggesting that the limiting effect of N on soil C sequestration would be intensified under W with P conditions. Our findings suggest that, without an increase in precipitation or concurrent P and W, the semiarid Inner Mongolian grasslands may potentially act as a net C source in the future. [Copyright &y& Elsevier]