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Abstract We investigate the effect of uncertainty in water vapor continuum absorption at terrestrial wavenumbers on CO₂forcing , longwave feedbackλ, and climate sensitivity at surface temperaturesT_sbetween 270 and 330 K. We calculate this uncertainty using a line‐by‐line radiative‐transfer model and a single‐column atmospheric model, assuming a moist‐adiabatic temperature lapse‐rate and 80% relative humidity in the troposphere, an isothermal stratosphere, and clear skies. Due to the lack of a comprehensive model of continuum uncertainty, we represent continuum uncertainty in two different idealized approaches: In the first, we assume that the total continuum absorption is constrained at reference conditions; in the second, we assume that the total continuum absorption is constrained for all atmospheres in our model. In both approaches, we decrease the self continuum by 10% and adjust the foreign continuum accordingly. We find that continuum uncertainty mainly affects through its effect onλ. In the first approach, continuum uncertainty mainly affectsλthrough a decrease in the total continuum absorption withT_s; in the second approach, continuum uncertainty affectsλthrough a vertical redistribution of continuum absorption. In both experiments, the effect of continuum uncertainty on is modest atT_s = 288 K (≈0.02 K) but substantial atT_s ≥ 300 K (up to 0.2 K), because at highT_s, the effects of decreasing the self continuum and increasing the foreign continuum have the same sign. These results highlight the importance of a correct partitioning between self and foreign continuum to accurately determine the temperature dependence of Earth's climate sensitivity.