The oxygen evolution reaction (OER) is a critical half-reaction in electrochemical water splitting; however, its sluggish kinetics necessitate the development of efficient, stable, and low-cost electrocatalysts. Transition-metal-based perovskite oxides are promising candidates owing to their earth-abundant composition, structural tunability, and versatile surface chemistry. In this study, SrCo_0.6Mn_0.4O₃ (SCM) perovskite oxides were synthesized via four different methods, such as solid state (SCM-SS), sol–gel (SCM-SG), co-precipitation (SCM-CP), and the hydrothermal method (SCM-HT). XRD and FESEM analyses confirmed the formation of crystalline perovskite oxides with distinct morphologies and crystallinities, directly influencing their electrocatalytic performance. Among all the samples, SCM-SS demonstrated the best activity, requiring an overpotential of 1.07 V at a current density of 10 mA cm^-2 and exhibiting the smallest Tafel slope of 145.82 mV dec^-1 in 1 M KOH. The overpotential values followed the following order: SCM-SS (1.07 V), SCM-SG (1.20 V), SCM-HT (1.22 V), and SCM-CP (1.35 V). Similarly, the Tafel slopes were SCM-SS (145.82 mV dec^-1), SCM-CP (151.46 mV dec^-1), SCM-SG (153.97 mV dec^-1), and SCM-HT (226.55 mV dec^-1). These findings highlight that the synthesis method plays a decisive role in tailoring crystallinity, morphology, and the electrocatalytic activity of SCM perovskites, offering valuable guidelines for designing next-generation water-splitting catalysts. This work contributes to advancing Sustainable Development Goal 7 by promoting clean energy technologies and supports Sustainable Development Goal 13 by addressing climate challenges through the development of efficient, sustainable electrocatalysts.