Forest litter is a large reservoir of organic compounds that adds CO2 to the atmospheric carbon pool when it decomposes. Predicting CO2 efflux from litter decomposition is difficult because litter can undergo significant diurnal and day-to-day shifts in temperature. Moreover, the relationship between temperature and respiration may change if the decomposer microorganisms acclimate to short-term temperature changes. Therefore, we studied the relationship between temperature and respiration by litter decomposer microorganisms in a Pinus resinosa (Ait.) system and tested the hypothesis that their respiration acclimates to temperature. We found only limited evidence for acclimation following 6 °C shifts for 7 days. This suggests that increase in respiratory CO2 loss associated with increased temperature would not be greatly ameliorated by physiological acclimation for periods of up to a week.