A new and efficient PdII‐catalyzed intermolecular annulation of N‐benzoylsulfonamide with allenes for the synthesis of 3,4‐dihydroisoquinolin‐1(2H)‐ones is reported. This CH functionalization is compatible with ambient air and moisture, and it can be applied to terminal or internal allenes with different synthetically attractive functional groups. Control experiments and a kinetic isotope effect study are conducted and a plausible mechanism is proposed. A new and efficient PdII‐catalyzed intermolecular annulation of N‐benzoylsulfonamide with allenes for the synthesis of 3,4‐dihydroisoquinolin‐1(2H)‐ones is reported (see scheme). This CH functionalization is compatible with ambient air and moisture, and it can be applied to terminal or internal allenes with different synthetically attractive functional groups. Control experiments and a kinetic isotope effect study were conducted and a plausible mechanism is proposed.