Most studies of the effects of litter mixing have focused on the decomposition in mixture of senescent leaves of different plant species. Previous research has shown that stream detritivores can benefit from the combined use of senescent and green leaves. We conducted a litter bag experiment in a stream to test the hypothesis that a mixtures of senescent and green leaves decomposed more rapidly, mediated by increased detritivore colonization, than leaves of each type in isolation. The observed abundances of two detritivore species, the amphipod Sternomoera rhyaca and the caddisfly Lepidostoma complicatum, in mixtures of senescent oak and green alder leaves were three to six times higher than expected on the basis of litter patches of each species alone. L. complicatum abundance also responded positively to the mixing of senescent oak and green maple leaves. Despite the synergistic effect of mixed senescent and green leaves on detritivore colonization, observed leaf mass loss in mixtures was not higher than the expected loss. Changes in the chemical properties of senescent and green leaves due to mixing may decrease the feeding rate of detritivores in mixtures because preferential or compensatory feeding occurred.