Bipolar disorder is a common psychiatric disorder characterized by mood fluctuations. Bipolar disorder is not a risk factor of cancer but bipolar patients often have lifestyle and daily habits that can increase the risk for cancer. When bipolar patients have been diagnosed with cancer, they need a sustained psychiatric follow-up and support because of the distress due to the diagnosis of cancer or to the side effects of some treatments used in oncology (corticotherapy, chemotherapy, interferon...), which can lead to a destabilization of mood and alter the treatment of cancer. Most people with bipolar disorder are prescribed psychoregulators, but these treatments have to be used with caution in the case of cancer comorbidity, keeping in mind their interferences and the cumulative effects with current cancer treatments. Consultation-Liaison psychiatrists play a major role in the follow-up and the surveillance of these patients, in collaboration with oncologists, general practitioners, and also patient’s families.