The partial widths of the fermionic Higgs-boson decays are calculated in the one-loop approximation of the minimal standard model of electroweak interactions. The soft-photon bremsstrahlung is resummed by means of Yennie-Frautschi-Suura exponentiation and the hard-photon spectrum is integrated analytically for a variable maximum photon energy. A general expression for the weak corrections in the modified on-mass-shell scheme is presented. For the charged-lepton and light-quark modes the formulae may be greatly simplified by neglecting the masses of all fermions, except for the top quark. For the b b and t t channels individual approximation formulae are derived assuming that the Higgs boson and the top quark are heavy as compared to the weak gauge bosons. Below the t t production threshold the electroweak corrections are generally at the few-percent level but for a 1 TeV Higgs boson they may become as large as 15%.