Ni-Ga alloy catalysts were synthesized by a surfactant-assisted co-precipitation method and were tested in CO2 hydrogenation to methanol at 10 bar and at ambient pressure. The presence of surfactant in the synthesis led to a decrease in particle size, with the catalyst produced using 1% of surfactant (C_1%) presenting the smallest and most homogeneous particle size. A difference between the catalysts was also observed in the change of the crystalline phase after the reaction, where the C_1% catalyst presented the lowest loss of the Ni5Ga3 active phase. Methanol productivity showed positive relations with smaller particle size and higher quantity of Ni5Ga3 crystalline phase remaining after the reaction, with the C_1% catalyst presenting the highest methanol productivity. Catalytic evaluation under different conditions showed that higher temperature and GHSV values led to poorer selectivity to methanol. The C_1% catalyst also presented good activity at ambient pressure and remained stable after 5 h, with no deactivation. A mechanistic study employing DRIFTS analyses found that the reaction pathway on Ni-Ga alloy involved both the RWGS and formate routes, as shown by the presence of formate, methoxy, and CO intermediates.