Abstract The increasing world energy demand has derived in the consumption of conventional sources of energy, leading to a rise in non-conventional resources such as heavy oils (HO). Nevertheless, the HO physicochemical properties such as high viscosity, are related to significant operational issues in production and transport processes. Thus, the main objective of this study is the HO viscosity reduction through a novel cracking reactions method prompted by an ultrasound cavitation technique assisted with nickel oxide nanoparticles functionalized over nanoparticulated silica (SiNi) as catalysts, and water as a hydrogen donor for enhancing the cracking reactions, fomenting the conversion of the crude oil heavy compounds (asphaltenes) into lighter sub-components. An HO with 17.02% of asphaltenes content was used for carrying out the tests. Along the study, there were identified several viscosity reduction mechanisms related with asphaltenes adsorption onto SiNi nanoparticles surface affecting the fluid internal structure, as well as the reduction of the crude oil asphaltenes content due to its conversion into lighter components. These mechanisms were widely explained by a phenomenological approach through rheological behavior measurements and modeling, which also provide a better understanding of the treatment effect in the HO mobility and an increased transport capacity. The viscosity measurements were realized upon nanoparticles and gasoline addition, and ultrasound cavitation separately. The ultrasound cavitation submission time was evaluated, with better results as the exposure time increased. The effect of nanoparticles concentration was also assessed, obtaining high degrees of viscosity reduction with nanoparticles dosages = 2000 mg/L. After the complete treatment application, an asphaltenes content reduction greater than 15% was observed with a viscosity reduction degree (VRD) up to 50% at a fixed shear rate of 20 s-1. This study should open a wider landscape about the use of nanotechnology for improving the production and transport of heavy oils.