Wildfires burn as much as 3% of Earth’s surface annually and remove carbon (C) stored in surface soils. Prescribed burns may offer an opportunity to preserve soil C stocks by limiting the extent and severity of wildfires. However, there is a limited number of days that are dry enough to conduct prescribed burns but wet enough to prevent the unintentional spread of fire. While prescribed burns mostly occur during the historical fire season—late summer and fall—burning during other favorable seasons, like spring, would facilitate forest management. Yet, it is not clear how burning in the spring versus the fall affects soil C stocks. To assess how burn season affects soil C dynamics, we measured bulk soil C, mineral-associated organic C (MAOC), particulate organic C (POC), pyrogenic organic matter (PyOM), microbial respiration, and extracellular enzyme activity in surface soils for two years after burning young mixed-conifer forest stands in either the fall or spring. We found that fall burning, which tended to consume more surface fuels, immediately combusted soil organic matter, lowering POC from 37 ± 14 to 14 ± 8.3 g C kg^-1 three days after burning. Furthermore, fall burning stimulated microbial respiration, preventing bulk C from increasing above 43 ± 14 g C kg^-1 for two years. Spring burning did not decrease soil C, and MAOC increased by 36%. Taken together, our results suggest that spring prescribed burns preserved soil C stocks relative to fall burns in young mixed-conifer forest stands.