Copper (Cu) is a recyclable, abundant, and promising catalyst for energy transition reactions like electrochemical conversion of nitrate (NO₃RR) and CO2 electroreduction. However, conventional Cu-based electrocatalysts struggle with activity, selectivity, and durability, especially under harsh electrochemical conditions. Exsolution—the in-situ generation of metallic nanoparticles on oxide supports in a single step—enables tightly anchored, size-controlled particles, enhancing stability and performance. Incorporating Cu into Sr1-α(Ti, Fe)O₃-γ perovskites, an earth-abundant system with mixed ionic-electronic conductivity and adequate oxygen vacancies, overcomes the limitations of traditional Sr(Ti, Fe)O₃ in facilitating nanoparticle exsolution. In this work, we demonstrate that incorporating Cu-doping into strontium-titanite-ferrite (STF) (Sr0.95Ti0.3Fe0.7-xCuxO3-γ) perovskites promotes the in-situ exsolution of well-dispersed Cu-nanoparticles with tunable properties. The designed material enables nanoparticle formation at temperatures as low as 400 °C within one hour, representing relatively mild temperature conditions and relatively fast exsolution compared to the literature. By varying the exsolution conditions, such as temperature and time, we demonstrate substantial control over nanoparticle characteristics, for example, particle size between ~13 and ~38 nm and population density between ~118 and 650 particles/μm2, allowing the tuning of catalytic activity for NO₃RR. These findings highlight the potential of Cu-doped perovskites as a versatile and sustainable platform for advanced catalytic applications.