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Organic–inorganic lead halide perovskite solar cells are regarded as one of the most promising technologies for the next generation of photovoltaics due to their high power conversion efficiency (PCE) and simple solution manufacturing. Among the different compositions, the formamidinium lead iodide (FAPbI₃) photoactive phase has a bandgap of 1.4 eV, which enables the corresponding higher PCEs according to the Shockley–Queisser limit. However, the photoactive crystal phase of FAPbI₃is not stable at room temperature. The most high‐performing compositions to date have reduced this problem by incorporating the methylammonium (MA) cation into the FAPbI₃composition, although MA has poor stability at high temperatures and in humid environments, which can limit the lifetime of FA_xMA_1−xPbI₃films. Cs_xFA_1−xPbI₃perovskites are also explored, but despite better stability they still lag in performance. Herein, the additive engineering of MA‐free organic−inorganic lead halide perovskites using divalent cations Sr²⁺and Ca²⁺to enhance the performances of Cs_xFA_1−xPbI₃perovskite compositions is explored. It is revealed that the addition of up to 0.5% of Sr²⁺and Ca²⁺leads to improvements in morphology and reduction in microstrain. The structural improvements observed correlate with improved solar cell performances at low additive concentrations.