Electrochemical energyEnergy conversion is critically significant within the energyEnergy technology area to provide a better and more sustainable future. Electrocatalysis lies at the center of clean energyEnergy conversion, and hence, it is expected to present further improvements in sustainable technologies. Among various possible materials trying to exhibit electrocatalytic activity, tin oxideTin oxide (SnO2) and its nanocomposites have been extensively investigated as promising materials for electrochemical energyEnergy conversion applicationsApplications because they have a specific structure and allow various functionalities. This chapter gives a comprehensive aspect on the SnO2-based electrocatalysts with a key focus on the electrochemical reactions they are intended for. We also discuss in detail the design and synthesis of SnO2 composites, especially the control of all possible properties in enhancing the performance of the alloys used in electrochemical energyEnergy conversion. Even with remarkable progress on the preparation of SnO2-based electrocatalysts, challenges have been recognized, and there exits gaps to further develop any promising future innovation to advance in enhancing their utilization and thus effectiveness.