This chapter reviews the definitions and backgrounds of human trafficking and sex work, and their relationship with mental health and psychological well-being, and concludes with a discussion on the way forward. The trafficking is the exploitation of human beings by means of sexual exploitation, forms of forced labour, slavery, servitude, or the removal of human organs through threat or use of force, coercion, abduction, fraud, deception, abuse of positions of power or vulnerability. Trafficking into sex work is a profound human rights violation that demands effective and comprehensive international action. Issues related to trafficking and sex work are the biggest priorities of the current world in terms of health, including sexual and reproductive health and HIV prevention, and the promotion of human rights and gender equality. Mainstreaming mental health and psychological well-being is the key to addressing the devastating human rights violations of human trafficking and sex work.