High prevalence and strong associations of chronic disease, poor sleep quality, poor mental health, and suicidal ideation (SI) have been reported worldwide. However, the underlying mechanism remains unexamined. The participants were 2646 Chinese medical college students with an average age of 20.13 years. Pittsburgh Sleep Quality Index, the Kessler Psychological Distress Scale, and SI was evaluated. The lifetime SI, past 12-month SI, and chronic disease prevalence rates were 10.0%, 8.4%, and 4.6%, respectively. The results of logistic regression analysis in this study found that chronic disease, self-reported poor sleep quality, poor mental health, gender and scholarship were associated with lifetime SI. Similar results were also found for 12-month SI with an exception of region. This result indicated that the effects of chronic diseases on the SI were mediated by self-reported sleep quality and mental health. Physical diseases, sleep-related concerns, and mental health issues need to be addressed through a multidisciplinary team approach and various delivery systems to prevent SI among medical college students.