The results of studies of the thermoelectric power of composites Cd3As2 + n mol % MnAs (n = 10, 20, 30, 44.7) at high pressures up to 50 GPa are presented. In the pressure range P = 28–35 GPa (n = 10, 20), at 20–35 GPa (n = 30), and in the range 30–35 GPa (n = 44.7), all the materials studied exhibit specific features in the behavior of the thermoelectric power S(P) (extrema, inflection points on curves or hysteresis). At a pressure exceeding 40 GPa, the thermoelectric power changes weakly or practically does not change both with an increase and with a subsequent decrease in pressure.