This study aimed to enhance the nutritional value and oxidative stability of fortified milk by investigating the properties of fish oil Pickering emulsion (FOPE) stabilized by selenium nanoparticles (SeNP) loaded-whey protein concentrate/phloretin (WPC/PHL) complex. Initially, the influence of SeNP concentration on the WPC/PHL complex was evaluated through measurements of particle size, antioxidant activity, and intermolecular interactions. Results demonstrated that increasing SeNP concentration from 0.1 % to 0.3 % significantly enhanced the antioxidant activity, with ABTS assay values rising from 42.87 % to 76.14 % and DPPH assay values increasing from 59.10 % to 86.11 %. FTIR and docking analyses confirmed the formation of bonds (hydrogen and van der Waals) between the WPC/PHL/SeNP nanoparticles. Subsequently, the FOPEs were characterized, revealing that increasing SeNP concentration reduced droplet size, indicating improved emulsion stability. Furthermore, the oxidative stability of the emulsions improved with increasing SeNP concentrations (0.1 % to 0.3 %), as evidenced by a decrease in peroxide value (PV) from 4.27 meq/kgO to 2.83 meq/kgO and a reduction in malondialdehyde (MDA) content from 86.61 mg/kg oil to 62.78 mg/kg oil after 10 days of storage. Finally, the oxidative stability of fortified milk containing these FOPEs was also significantly enhanced. These findings provide a novel perspective on developing SeNP as an antioxidant particle, potentially suitable for formulating functional emulsified food products susceptible to oxidative deterioration.