To better understand the contribution of alpine lakes to global CO2 emissions, carbon dioxide concentrations and fluxes to the atmosphere were measured in five high‐elevation lakes and five reservoirs in the Sierra Nevada, California. Median summer surface concentrations of dissolved CO2 (reservoirs: 21.1 μM, lakes: 23.7 μM) were supersaturated for most of the ice‐free season. Median diffusive flux of CO2 was low as compared to other inland waters (lakes: 260 mg CO2 m−2 d−1, reservoirs: 192 mg CO2 m−2 d−1). Linear mixed modeling demonstrated that the length of ice cover, persisting for 5–9 months and allowing for accumulation of under‐ice CO2, was a strong predictor of summer surface CO2. During the ice‐free period, surface evasion of CO2 was highest for the first 40 d after ice‐off when carbon dioxide that had accumulated during winter was released, although supersaturation and evasion continued until fall at most sites despite low rates of ecosystem metabolism. This study suggests that the contribution of high‐elevation, oligotrophic lakes and reservoirs in the Sierra to global CO2 emissions are small despite persistent supersaturation, and are primarily driven by the duration of ice cover.