The purpose of this study was to experimentally confirm the probiotic properties and antioxidant activity of plant fermented beverages stabilized with microemulsion. The object of the study were beverages obtained from hemp seeds and fermented with Bifidobacterium longum. To stabilize the plant base, the microemulsion with a bioactive substance (curcumin) was introduced with simultaneous ultrasound treatment. A significant increase in the viscosity of beverages with microcellulose-stabilized microemulsion was noted. Non-fermented plant beverages are characterized by their smaller diameter and distribution of particles in the micro-range, from 0.81 to 6.5 µm. When Twin-stabilized microemulsion was added to beverages, a monodisperse distribution of particles sufficiently small in diameter was observed. A significant increase of 29.4–33.6% in the antioxidant activity of plant beverages stabilized by ME with curcumin was established. A maximum concentration of flavonoids was noted in non-fermented plant beverages containing microemulsion. The results of this study proved the possibility of obtaining fermented plant beverages with identified probiotic and antioxidant properties. A positive effect of stabilizing with a microemulsion loaded with biologically active components on the development of probiotic microorganism cultures in the system of fermented plant products and the formation of their antioxidant activity was established.