Abstract <p>Samples of a magnetic fluid stabilized with a double surfactant layer have been synthesized in water using a nonionic stabilizer TWEEN 20 (Polysorbate 20) as the second layer. The rheological properties of the synthesized samples have been studied as depending on their concentration. In contrast to fluids containing dissociated surfactants, the viscosity of the magnetic fluid decreases with increasing temperature faster than does the viscosity of the base medium (water). The main advantage of using a nonionic surfactant is the possibility of synthesizing low-temperature magnetic fluids based on water–alcohol mixtures and aqueous salt solutions. Fluids stabilized with TWEEN 20 in ethylene glycol and propylene glycol solutions remain mobile to temperatures of –40 and –50°С. When calcium chloride (CaCl₂) solutions are used as base media, the test samples of the fluid retain their working capacity to a temperature of –30°С. Magnetic fluids based on alcohol and salt solutions can be indispensable in the fields of engineering, in which their high fire and environmental safety are required. The chemical inertness of particles stabilized with TWEEN 20 makes them to be applicable in biology and medicine.</p>