Dry reforming of methane is a promising chemical reaction that can utilize CO2 and natural gas to produce value-added feedstocks. However, this process's commercialized implementation has been stalled due to the lack of excellent durable and reusable catalysts. Here, we report a pseudo-binary alloy (Ni0.5Co0.5)3Ge/SiO2, which partially substitutes Ni with Co without altering the parent Ni3Ge phase. The combination of high-angle annular dark-field–scanning transmission electron microscopy–energy-dispersive system, X-ray diffraction, and X-ray absorption fine-structure analysis showed the formation of a pseudo-binary alloy structure. High catalytic activity with remarkable thermal stability is produced by alloying Ni with Co and Ge during continuous operation of 1000 h (mean catalyst life: τ = 1300 h) at 700 °C even below the equilibrium conversion. Detailed characterization and theoretical calculations revealed that doping Co to Ni3Ge optimally modified the C–H activation ability, which minimized coke formation for high stability.