Octahedral Pt3Ni on carbon support (Pt3Ni/C) is well-known to be excellent electrocatalysts for the oxygen reduction reaction (ORR) due to its exceptional activity. However, their long-term stability is poor, since the octahedral shape is entirely shattered and Ni is simply leached out during operation. To improve activity and stability, third metals M (i.e., Ga, Ag, Cu, Rh, Co, Fe, and Mo) were added to Pt3Ni electrocatalysts by gas-phase synthesis using two distinct approaches referred to as Co-impregnation (Pt3Ni-M/C) and Metal-doping (M-Pt3Ni/C). The size distributions of octahedron and truncated octahedron were almost identical, with an average particle size of around 8–9 nm for both approaches. The Fe–Pt3Ni/C exhibited the highest pristine ORR activity in terms of both mass activity (1.64 A mgPt−1) and specific activity (65.7 A mgPt−1), which were 2.8 times greater than Pt3Ni/C and 27.3 times more than commercial Pt/C catalyst. For an accelerated durability test (ADT) of 16,000 cycles, the Cu–Pt3Ni/C exhibited the most stable catalysts with an activity retention of 69.9%, followed by Ga-Pt3Ni (61.7%) and Rh–Pt3Ni (52.2%). The Cu–Pt3Ni/C catalyst was 5.8 times more stable than the Pt3Ni/C catalyst. When the same metal was used, it was discovered that the Metal-doping (M-Pt3Ni/C) approach provided superior ORR activity and stability than the Co-impregnation (Pt3Ni-M/C) technique.