Ultrafast photoinduced electron transfer (PET) from N,N-dimethylaniline (DMA) to coumarin dyes in a room-temperature ionic liquid (RTIL, [pmim][BF 4]) and in a mixed micelle containing the RTIL and a triblock copolymer, (PEO)20-(PPO)70-(PEO)20, (Pluronic P123) is studied using femtosecond upconversion. A Marcus-like inversion in the rate of PET is observed in neat RTIL. This is attributed to high viscosity and nanostructuring of the RTIL. Diffusion and the rate of PET in the neat RTIL are slower than those in the RTIL-P123 mixed micelle. The coumarin dyes exhibit faster electron transfer and translational diffusion (anisotropy decay) in the RTIL-P123 mixed micelle compared to that in the P123 micelle. © 2011 American Chemical Society.