The creation of anodic ethanol oxidation reaction catalysts with superior all-around performance for direct ethanol fuel cells (DEFCs) has continued to attract the attention of researchers. An ultrathin trimetallic PtAuBi aerogel with branching, rough-surfaced 1D nanowires that self-assemble into a 3D porous network structure has been created in this study. It has a mass activity (MA) of 8045 mA mgPt−1 in an alkaline medium, which is 7.56 times greater than that of commercial Pt/C (1064 mA mgPt−1). Notably, the catalytic activity and resistance to CO poisoning of PtAuBi aerogels are improved by the addition of an efficient “active additive” Au. The results analysis reveals that the increased performance of PtAuBi aerogel is mostly attributable to the integrated function of the 3D porous network structure, the downward shift of the Pt d-band center, and the synergistic effect of the “Pt–Bi” and/or “Pt–Au” dual active sites.