Solution‐processed, self‐organized multiple quantum well (MQW) perovskites possess good film coverage and high photoluminescence quantum efficiency, which are promising for high performance light‐emitting diodes (LEDs). However, due to the inclusion of insulating large organic cation as barrier layer, the charge transport in MQW perovskites is not as efficient as 3D perovskites, which limits the improvement of power conversion efficiency of MQW perovskite LEDs. Here, it is demonstrated that by molecular engineering, the conductivity of MQW perovskite film can be effectively increased by reducing the barrier width in QWs, thus leading to enhanced device performance. By controlling the constitution of the narrow‐barrier‐width MQW perovskites, one can achieve green LEDs with a high luminance of 30 000 cd m−2 at a low voltage of 6 V and a peak external quantum efficiency of 7.7%. Moreover, the green perovskite LEDs show a lifetime of 63 min with initial luminance of 1330 cd m−2, representing one of the best performing green perovskite LEDs. Here, a promising strategy is provided to further boost the efficiency, brightness, and stability of MQW perovskite LEDs. The barrier width of multiple quantum well (MQW) perovskite is controlled through molecular engineering of the large organic cation. MQW perovskite films based on a novel benzimidazolium exhibit reduced barrier width and enhanced conductivity, leading to green perovskite light‐emitting diodes with high luminance and good stability.