The rate constants of low‐energy electron attachment to BCl3diluted in N2are measured as a function ofE/Nat 1–11 Td, corresponding to mean electron energies at 0.4–1.0 eV. The negative ions produced by hollow‐cathode discharges of either pure BCl3or mixtures of BCl3in N2are mass analyzed to identify the products of electron attachment to BCl3. Only Cl−ion is found in the discharge media, although BCl−3is observed at the applied voltage significantly lower than the breakdown voltage. The electron attachment processes of BCl3are discussed.