Oil-in-water (O/W) nanoemulsions based on nonionic ethoxylated polymeric surfactants were prepared and evaluated for demulsification of water/oil emulsions and model asphaltene emulsions. The nanoemulsions were prepared using two nonionic ethoxylated polymeric surfactants with different numbers of ethylene oxide units in their chains and the solvents xylene and Solbrax as the oil phase, at different concentrations. The interfacial properties of the different systems applied in the demulsification process were evaluated in model emulsions and were correlated with their ability and/or speed of diffusion to the interface. Tests of asphaltene dispersion/flocculation were performed to evaluate whether the nanoemulsions change the aggregation state of asphaltenes during the demulsification process. The results of gravitational separation tests showed that the new nanoemulsion formulations studied can be applied to demulsify water/oil emulsions. Both the type of polymeric surfactant used and the type and content of the oil phase in the nanoemulsions had a significant influence on the efficiency and speed of breaking down emulsions. The efficiency was related to the surfactant hydrophilicity and the solubility parameter of the oil phase, which also affected the size of the asphaltene aggregates.