Methane hydroxylation at the dinuclear copper site of particulate methane monooxygenase (pMMO) is studied by using density functional theory calculations. The electronic, structural, and reactivity properties of a possible dinuclear copper species (mu-oxo)(mu-hydroxo)(CuCuIII)-Cu-II are discussed with respect to the C-H bond activation of methane. We propose that the tyrosine residue in the second coordination sphere of the dicopper site donates an H atom to the mu-eta(2):eta(2)-peroxoCu(II)Cu(II) species and the resultant (mu-oxo)(mu-hydroxo)(CuCuIII)-Cu-II species can hydroxylate methane. This species for methane hydroxylation is more favorable in reactivity than the bis(p-oxo)(CuCuIII)-Cu-II species. The H-atom transfer or proton-coupled electron transfer from the tyrosine residue can reasonably induce the O-O bond dissociation of the mu-eta(2):eta(2)-peroxoCu(II)Cu(II) species to form the reactive (mu-oxo)(mu-hydroxo)(CuCuIII)-Cu-II species, which is expected to be an active species for the conversion of methane to methanol at the dicopper site of pMMO. The rate-determining step for the methane hydroxylation is the C H cleavage, which is in good agreement with experimental Km values reported so far.