Purpose In this study, we investigate association of biological rhythm impairment with levels of anxiety, depression and dream anxiety and other sociodemographic correlates of Baskent University medical students. Methods 193 students who accepted to participate in the study from Baskent University School of Medicine Grades 1, 2, 3, 4 and 5, were enrolled to our study. Participants were administered the Beck Anxiety Inventory, Beck Depression Inventory, Dream Anxiety Scale, Biological Rhythm Scale and Sociodemographic Data Form. Results Participants’ biological rhythm (impairment) scores were found to be significantly associated with the Dream Anxiety Scale, Beck Depression Inventory and Beck Anxiety Inventory scores. Female students were found to have higher biological rhythm, activity rhythm, sleep rhythm, anxiety and dream anxiety scores, which means that they have higher anxiety levels and more impaired biological rhythms. Students who drowse in the lectures were found to have higher sleep, activity, social and dominant rhythm patterns with higher levels of dream anxiety and Beck Depression Inventory scores as well. Conclusions Biological rhythm impairment is related to dream anxiety, anxiety and increased depression levels. Smoking, alcohol consumption and having pet are factors negatively effecting biorhythms and increasing dream anxiety in medical students. Drowsing during the lectures is a common complaint of medical students and can be a sign of irregularity in the biological rhythms and psychiatric disorders like anxiety and depression as well. Encouraging medical students for having more regular biorhythms can help them ensuring their own mental health.