Homogeneous platinum alloy nanoparticles (NPs) are of great interest to the electrocatalytic community for potential use in various fuel cell electrodes. Increasing the surface area available per unit mass by decreasing the size of NPs while maintaining or improving activity is one of the key tasks of fuel cell catalysis. Achieving both in a synthesis of multielement NPs is still a challenging workup. In this investigation, we report the use of glycine as a size control agent to make ultrasmall homogeneous trimetallic PtNiCu NPs within 2-5 nm range. The mechanistic roles of dimethyl formamide (DMF), formaldehyde, water, and glycine are explored to understand the formation of these small NPs. Interestingly, it was observed that these PtNiCu NPs exhibited substantially enhanced mass activities toward the electro-oxidation of ethanol in comparison to commercial Pt black.