Photochemical reactions of duroquinone (DQ) in solutions consisting of mixtures of the ionic liquid N-butylpyridinium tetrafluoroborate ([BPy][BF4]) and acetonitrile (MeCN) were studied using the 355 nm laser flash photolysis technique. Increasing the ratio of [BPy][BF4] had no obvious impact on the absorption peak of the triplet excited state of DQ (3 DQ *), which followed monoexponential kinetics in the N2-saturated solution. However, increasing the ratio of [BPy] [BF4] did affect the photoinduced electron transfer process from triethylamine to 3 DQ * in the mixture by decreasing the reaction rate and the quantum yield of the transient radical. The results highlight the ability to tune the efficiency and the rate of the photoinduced electron transfer by changing the proportion of [BPy][BF4] in the mixture.