Ni-Fe catalysts supported on gamma-Al2O3 and HZSM-5 were proved to be active for fatty acids conversion into hydrocarbon fuel. The strong interaction between Ni and gamma-Al2O3 produced NiAl2O4 species without the Ni-Fe alloy on 10% Ni-5%Fe/gamma-Al2O3, while the weak interaction between Ni and HZSM-5 induced FeNi3 alloy formation along with Ni and NiFe2O4 on 10%Ni-5%Fe/HZSM-5. On the two catalysts, palmitic acid could be completely converted. However, the hydrocarbon selectivity was obviously different, with pentadecane and hexadecane mainly obtained with a selectivity of 72.2% on 10% Ni-5%Fe/gamma-Al2O3 and 60.5% on 10%Ni-5%Fe/HZSM-5, respectively, which were attributed to the formation of different active species. Detailed studies suggested that the surface of NiAl2O4 species favored the decarboxylation (DCO2)/decarbonylation (DCO) pathway to produce pentadecane, whereas the FeNi3 alloy facilitated the hydrodeoxygenation (HDO) pathway to produce hexadecane. This work offers an effective approach to tuning the hydrocarbon selectivity by using different interactions between metals and supports.