In this work, we probe the effect of NiFe2O4 nanoparticles (NPs) as catalysts in heavy crude oil upgrading in low hydrogen/feedstock ratio, that can occur in places where the conditions cannot be controlled, such as inside oil reservoir. The NPs were synthesized by the thermal decomposition method of metal precursors. In order to obtain the NPs, the decomposition of nickel and iron acetylacetonate was done in presence of oleic acid and oleylamine, which worked as solvents, and stabilizing and reducing agents (the solution was heated to 200 degrees C for 2 h and then, heated to reflux to 300 degrees C for 30 min).The produced NPs were characterized by UHR-FE-SEM and spherical aberration-corrected STEM. These techniques revealed the formation of nanoparticles with an average size of 10 +/- 1.7 nm and the determination of the crystalline arrangement of the nanomaterials. Additionally, XRD confirmed that nanoparticles corresponded to the crystallographic phase (NiFe2O4). The experiments were performed in a batch reactor at an initial 100% H-2 pressure of 45 Kgf. cm(-2) and 380 degrees C, during 1 h at 500 rpm. NiFe2O4 NPs increased the upgrading of heavy oil, evaluated by viscosity, API gravity, sulfur and nitrogen removal, and simulated distillation analysis; residue conversion was approximately 28% and sulfur removal reached values of up to 20%. The analysis of spent catalyst by XPS showed that the iron sulfide phase (FeS) was formed.