The effects of micellization on the rate constants and Gibbs energy of electron transfer (ΔG et) are studied by time-resolved luminescence quenching of tris(2,2‘-bipyridyl)ruthenium(II) (RUBIPY) and pyrene (PY) by electron acceptors and donors in sodium dodecylsulfate (SDS) micelles. For RUBIPY, which is bound to the SDS micelles and accessible to water, ΔG et is considerably smaller than what is found in organic solutions, though the spectral properties of RUBIPY and the value of diffusion-controlled quenching rate constant are typical for the micellar interior. For this system, dissolution in micelles enables a change of the local reactant concentration and mobility, retaining their higher reactivity in aqueous solution. In contrast, for PY, which is known to be localized in the palisade layer of an SDS micelle, the quenching rate constants coincide well with those found in acetonitrile.