Sexual dysfunction is highly prevalent among people with mental health disorders (substance use disorders are also be included). Not only mental diseases and their correlates are associated with sexual dysfunction, but also their treatment, such as antidepressants, antipsychotics and methadone maintenance treatment (for opioid dependence), have been proven to have detrimental effects on sexual function. Sexual dysfunction as an adverse effect could be the reason of poor treatment adherence. In Asian culture, it still remains a taboo topic, and patients are unlikely to discuss their sexual problems with a medical specialist. This review aims to be a reminder that psychiatrists should go through this important issue comprehensively in the treatment process.