Cariprazine is a novel atypical antipsychotic drug that is widely used for the treatment of schizophrenia and bipolar mania/mixed disorder. We used the whole-cell patch-clamp technique to investigate the effects of cariprazine on hERG channels that are stably expressed in HEK cells. Cariprazine inhibited the hERG 1A and hERG 1A/3.1 tail currents at -50 mV in a concentration-dependent manner with IC50 values of 4.1 and 12.2 μM, respectively. The block of hERG 1A currents by cariprazine was voltage-dependent, and increased over a range of voltage for channel activation. Cariprazine shifted the steady-state inactivation curve of the hERG 1A currents in a hyperpolarizing direction and produced a use-dependent block. A fast application of cariprazine inhibited the hERG 1A currents elicited by a 5 s depolarizing pulse to +60 mV to fully inactivate the hERG 1A currents. During a repolarizing pulse wherein the hERG 1A current was deactivated slowly, cariprazine rapidly and reversibly blocked the open state of the hERG 1A current. However, cariprazine did not affect hERG 1A and hERG 1A/3.1 channel trafficking to the cell membrane. Our results indicated that cariprazine concentration-dependently inhibited hERG 1A and hERG 1A/3.1 currents by preferentially interacting with the open states of the hERG 1A channel, but not by the disruption of hERG 1A and hERG 1A/3.1 channel protein trafficking. Our study examined cariprazine's mechanism of action provides a biophysical profile that is necessary to assess the potential therapeutic effects of this drug.