Background To examine barriers to initiation and continuation of mental health treatment among individuals with common mental disorders. Methods Data are from the WHO World Mental Health (WMH) Surveys. Representative household samples were interviewed face-to-face in 24 countries. Reasons to initiate and continue treatment were examined in a subsample (n= 63,678) and analyzed at different levels of clinical severity. Results Among those with a DSM-IV disorder in the past twelve months, low perceived need was the most common reason for not initiating treatment and more common among moderate and mild than severe cases. Women and younger people with disorders were more likely to recognize a need for treatment. Desire to handle the problem on one’s own was the most common barrier among respondents with a disorder who perceived a need for treatment (63.8%). Attitudinal barriers were much more important than structural barriers both to initiating and continuing treatment. However, attitudinal barriers dominated for mild-moderate cases and structural barriers for severe cases. Perceived ineffectiveness of treatment was the most commonly reported reason for treatment dropout (39.3%) followed by negative experiences with treatment providers (26.9% of respondents with severe disorders). Conclusions Low perceived need and attitudinal barriers are the major barriers to seeking and staying in treatment among individuals with common mental disorders worldwide. Apart from targeting structural barriers, mainly in countries with poor resources, increasing population mental health literacy is an important endeavor worldwide.