<p>Organic–inorganic halide perovskite solar cells (PSCs) have emerged as a highly promising photovoltaic technology, owing to their high light-to-electric conversion efficiency. However, as the core functional structure of PSCs, perovskite typically exhibits a polycrystalline structure with some defects on its surfaces and grain boundaries. These defects usually lead to non-radiative recombination of photo generated electron–hole pairs and induce irregular ion migration, which severely reduce the power conversion efficiency (PCE) and long-term stability of PSCs. Thus, it is a critical challenge to effectively improve PCE and stability of PSCs by reducing these defects at the interfaces and grain boundaries of perovskite. Encouragingly, the modulation strategies toward these defects have been certificated to be effective approaches to address this issue. In this review, the common types of defects in perovskite of PSCs and their detrimental effects on performance of PSCs were systematically summarized. Subsequently, recent advancements in defect passivation techniques focusing on the upper interface, the buried interfaces and the precursor ink of perovskite were discussed. Finally, future research directions for interface defect passivation strategies aiming to provide insights for the development of high-performance and stable PSCs were outlined.</p>