Although the power conversion efficiencies (PCEs) of perovskite solar cells (PSCs) have made great progress, the surface and interface defects still affect their PCE and stability and hinder the commercialization. To overcome this problem, 1‐methylimidazole (1‐MIm) and 1‐methylbenzimidazole (1‐MBIm) were used as the interfacial passivation agents to passivate the defects at surface and interface. The results indicated that, in contrast to 1‐MIm, 1‐MBIm displayed a stronger Lewis coordination interaction with the uncoordinated Pb2+ to reduce the non‐radiative recombination and also effectively improved the charge transfer capacity of perovskite films due to its strong π–π conjugate interaction, resulting in the better photovoltaic performance. As a result, the PCE of the champion 1‐MBIm PSC was improved from 19.48 (pristine) to 21.22 % with a dramatically enhanced open‐circuit voltage (Voc=1.15 V). More importantly, a significant improvement in long‐term stability was achieved for 1‐MBIm perovskite devices, which was attributed to the high‐quality perovskite film caused by the strong passivation effect of 1‐MBIm and the hydrogen bond with water molecules. The results offers an efficient and facile strategy by interface engineering to fabricate high‐performance and stable PSCs for commercial application. Passivation agent: 1‐Methylbenzimidazole (1‐MBIm) as interfacial passivation agent can effectively enhance the charge transfer capacity and passivate the defects at surface and interface due to the strong π–π conjugate effect. As a result, the 1‐MBIm perovskite device displays an improved power conversion efficiency from 19.48 to 21.22 % with a dramatically enhanced open‐circuit voltage and significantly improved stability against humidity, heat, and UV light.