Water-in-oil emulsions are formed during petroleum production. These emulsions are stabilized by natural emulsifiers present in the oil, such as asphaltenes, resins, and paraffins, making their separation difficult. Various treatments can promote the breakdown of these emulsions, among them demulsification, which involves the addition of demulsifiers to promote separation of the water and oil phases. This work proposes the synthesis of demulsifiers by modification of branched polyethylenimine with the introduction of different non-ionic surfactants along the chain. Specifically, we used ethoxylated surfactants based on lauryl acid and nonylphenol, with different numbers of ethylene oxide units in their chains. The modified polymers were characterized by proton nuclear magnetic resonance spectroscopy and solubility tests. Demulsifier systems were prepared by dissolving the additives in two solvent mixtures: xylene/ethanol and xylene/butylglycol. These systems were applied in demulsification tests and evaluated by measuring the water-oil interfacial tension. The results showed that the additives did not significantly alter the interfacial tension values of the systems but were able to destabilize the emulsions, promoting water-oil separation.