Bipolar disorder in pregnancy was treated with nimodipine, because of lithium-induced nephrogenic diabetes insipidus. A 33-year-old primigravida woman at approximately 22 weeks 6 days of gestation had increasing blood pressure since 16 weeks of gestation, despite methyldopa 500 mg twice daily. She also had hypothyroidism and bipolar disorder, which were treated with levothyroxine and lithium carbonate, respectively. Nephrogenic diabetes insipidus developed, presumably because of chronic lithium exposure in high doses. She did not tolerate carbamazepine (the other agent commonly used for bipolar disorder in pregnancy). Thus, nimodipine was tried and tolerated well; furthermore, it was very effective in controlling her bipolar disorder. Nimodipine successfully controlled the bipolar disorder of a woman during pregnancy, who was intolerant of more commonly used agents.