[en] Efficient manipulation of crystallization and control over defects are crucial for optimizing the performance and durability of perovskite solar cells (PSCs). In this study, a novel organic multifunctional additive, 2-(furan-3-yl)ethanamine hydrochloride (FFEACl), is introduced which plays a pivotal role in regulating the crystallization process of FAPbI${}_3$. Incorporating FFEACl into the perovskite precursor solution effectively suppresses the formation of undesirable non-perovskite phase impurities while promoting the oriented crystallization of the $\mathrm{\alpha <!--\; ??\; -->}$-phase FAPbI${}_3$. Moreover, the addition of FFEACl leads to a more uniform surface potential and reduced defect density in the resulting FAPbI${}_3$ film. Consequently, the top-performing PSC exhibits an impressive power conversion efficiency (PCE) of 25.41%, along with enhanced operational stability. Notably, the fabricated PSCs maintain over 80% of their initial PCE even after 1000 h of continuous operation under one-sun illumination. The findings present a facile and effective strategy for fabricating perovskite photovoltaic devices with exceptional performance and long-term reliability. (© 2024 Wiley‐VCH GmbH)