Reduction of 2‐benzyl‐1‐mesityl‐5,7‐dimethyl‐2,3‐dihydrophosphindole 1‐oxide (2‐O), which was prepared by catalytic addition of dimesitylphosphane oxide across phenylacetylene via dimesityl‐phenylethenylphosphane oxide (1), with excess of trichlorosilane in toluene yielded 2‐benzyl‐1‐mesityl‐5,7‐dimethyl‐2,3‐dihydrophosphindole (2). Straightforward oxidation of 2 with sulfur and selenium in toluene at 110 °C allowed the isolation of crystalline colorless 2‐benzyl‐1‐mesityl‐5,7‐dimethyl‐2,3‐dihydrophosphindole 1‐sulfide (2‐S) and 1‐selenide (2‐Se). The hindered rotation of the P‐bound mesityl group around the P–C bond is indicative of significant intramolecular steric strain. Despite this strain, the P–E bond lengths (E = S, Se) lie in expected ranges.