Direct methanol fuel cells (DMFCs) have been considered as an ideal “green” energy converter because of their high energy-conversion efficiency and low pollution emission, while the high costs and poor poisoning tolerance of anode platinum catalysts have greatly hindered the large-scale commercialization of DMFCs. Herein, we report the stereoassembly of 3D porous Pt-on-Pd bimetallic nanodendrites on a 2D ultrathin Ti₃C₂T_x MXene matrix (Pt-on-Pd/Ti₃C₂T_x) through a convenient bottom-up approach. Interestingly, such a unique MXene-supported bimetallic heterostructure consists of a dense array of oriented Pt nanobranches on a Pd core, which endow the hybrid system with numerous accessible electrocatalytically active sites as well as optimized electronic structures. As a result, the obtained Pt-on-Pd/Ti₃C₂T_x catalyst exhibits superior electrocatalytic properties toward methanol oxidation, including a large electrochemically active surface area, a high mass/specific activity, and reliable long-term durability, and is far superior to conventional Pt/carbon black, Pt/Ti₃C₂T_x, Pt/graphene, and Pt/carbon nanotube catalysts. Density functional theory calculations further reveal a significant down shift of the d-band centers and weaker CO adsorption ability for the Pt-on-Pd/Ti₃C₂T_x model, thereby affording much stronger poisoning tolerance as well as dramatically enhanced methanol oxidation activity.