The development of efficient methods for trans-selective vicinal dideuteration remains an important yet challenging goal. We report a synergistic strategy that combines base-promoted H/D exchange of cyclopropenes with photoinduced radical addition, employing diarylphosphine oxides or glyoxylic acids as radical precursors and D2O as the sole deuterium source. Under mild conditions, a wide range of substituted cyclopropenes and radical precursors are well tolerated, delivering trans-dideuterated cyclopropyl phosphine oxides and carbonylated cyclopropanes in moderate to excellent yields with high deuterium incorporation.