Introduction: The course of bipolar disorder (BD) is characterized by relapse and remission periods. Although the symptoms show a significant and sometimes almost complete improvement during remission, the patients' functioning levels may be lower compared to the premorbid period. This study aimed to compare the functional levels between patients with BD during remission period and healthy controls and to evaluate the factors related to the functional status of the patients. Methods: In this cross-sectional study, functioning levels of the BD-I patients, who were in remission for three months or longer, were compared with those of the healthy controls. Young Mania Rating Scale and Hamilton Depression Rating Scale were used to determine remission status, and Bipolar Disorder Functioning Questionnaire (BDFQ) was used to determine the level of functioning. Results: The study included 165 BD-I patients during remission and 63 healthy controls. The BDFQ scores of the patients including intellectual functioning, sexual functioning, feeling of stigmatization, introversion, relationships with friends, participation in social activities, daily activities and hobbies, and taking initiative were found to be statistically significantly lower than those of the controls. When the functioning comparisons were carried out within the patients considering the drugs they were using, the functioning levels including domestic functioning and introversion domains were found to be significantly impaired in those who use at least one antipsychotic in addition to the mood stabilizers than in those who use only mood stabilizers. Conclusion: In BD, the impairments within multiple functioning domains are observed even during remission periods. Besides targeting remission through pharmacological treatment, psychosocial interventions for functioning are also important in the treatment of these patients.