We investigate the Seebeck and Nernst effects of pyrochlore iridium oxides (Nd_{1− x}Pr _x)₂Ir₂O₇ across the thermally induced and magnetic field-induced metal–insulator and topological transitions. Nd₂Ir₂O₇ exhibits the salient temperature dependence of the Seebeck coefficient accompanied by the enhancement of the Nernst effect in the vicinity of the thermal magnetic transitions. Moreover, the Seebeck coefficient shows a remarkable magnetic field hysteresis with the differential magnitude reaching as large as 110 μV/K, as the conductive magnetic domain walls are generated/annihilated by the external field. For x = 0.5, the Nernst signal increases rapidly across the field-induced metal–insulator transitions, exceeding the values reported in existing ferromagnetic oxides. These findings indicate that the thermoelectric effects increase significantly near the topological electronic phase transitions in strongly correlated systems, providing a new guideline for thermoelectric material design.