Autonomic nerve system is considered to be involved in bipolar affective disorder (BAD) or to be influenced by valproate monotherapy or valproate plus lithium combination. We planned to assess the effects of medication on atrial and ventricular conduction. The electrocardiography records were performed with eligible 15 patients with valproate, 20 patients with lithium-valproate combination use in euthymic phases of BAD and 20 healthy participants. The blood valproate and lithium concentrations in groups were in normal range. The difference in P maximum, P minimum, maximum QTc were statistically insignificant. Minimum QTc (F = 6.36; df = 2; P = 0.003) and QT dispersion (QTD) (F = 5.57; df = 2; P = 0.006) were statistically significant among the groups. There were no significant differences between patient groups among ECG parameters. Minimum QTc was significantly longer in combination group than healthy controls, whereas the QTD values in both patient groups were significantly lower than controls'. Valproate might have some preventive effects on ventricular electrical conduction because of lower QTD in both patient groups. Thus, valproate seems to have cardiac conduction stabilizing effect beside its mood stabilizing aspect. However, this finding needs replication and further corroboration in well-designed studies.