This study was intended to investigate physico‐chemical, rheological, and emulsifying properties of oil‐in‐water emulsions prepared from the Kluyveromyces marxianus mannoprotein (KMM). Also, the stress‐response function of the KMM emulsions was compared with that of the whey protein concentrate (WPC) emulsions in terms of zeta potential, size, and rheology. The stress experiments were conducted at different pH (3 to 9), ionic composition (0 to 500 mM NaCl), and temperatures (30 to 90 °C). The extracted KMM with a molecular weight of 107.2 kDa had 28.8% proteins and 68.22% carbohydrates. With increasing the KMM concentration to 1.5% (w/w), the zeta potential, droplet size, and apparent viscosity of the emulsions reached −35 mV, ∼1 μ, and ∼9 mPa·s, respectively. After applying pH, ionic composition, and temperature, the KMM emulsions were more stable than the WPC emulsions. In conclusion, KMM can be used as a bioemulsifier and be more effective in stabilizing emulsions than WPC.Practical ApplicationYeasts are a rich source of natural materials. In this study, we extracted mannoproteins from the yeast cell wall and evaluated their functional properties to be used as an emulsifier in oil‐in‐water emulsions. The results of this study confirm that the yeast‐derived mannoproteins are good at stabilizing these emulsions either in the presence or absence of different environmental conditions.