The results of experimental studies of the resistivity, Hall effect, and magnetoresistance of Cd3As2 + kMnAs composites (k = 20, 30, 44.7 mol %) in a toroid-type high-pressure chamber, which makes it possible to create a hydrostatic pressure up to 9 GPa at room temperature in magnetic fields up to 5 kOe, are presented. With increasing pressure, the electrical resistance of samples with different manganese contents is shown to increase at different rates. In the pressure range 4.2–4.4 GPa, a reversible structural transition is observed. An increase in pressure suppresses the positive component of the magnetoresistance; at pressures of P ≈ 1.0 and P ≈ 2.6 GPa, a region of negative magnetoresistance is observed. With a further increase in pressure, the magnetoresistance increases nonmonotonically up to Р ≈ 4.3 GPa, i.e., the phase transition region. © 2023, Pleiades Publishing, Ltd.