Higgs decays to gauge boson pairs are a crucial ingredient in the study of Higgs properties, with the decay H → γγ being particularly sensitive to new physics effects. Assuming all potential new physics occurs at energies far above the weak scale, deviations from standard model predictions can be parametrized in terms of the coefficients of a standard model effective field theory (SMEFT). When experimental limits on the SMEFT coefficients reach an accuracy of a few percent, predictions must be done beyond the lowest order in the SMEFT in order to match theory and experimental accuracy. This paper completes a program of computing the one-loop electroweak SMEFT corrections to H → VV', V = W+, Z, γ. The calculation of the real contribution to H → W+W-γ is performed by mapping two-loop amplitudes to the three-body phase space.