Many young people with mental disorders are not identified until some years after the first onset of symptoms and then frequently do not receive professional intervention. One promising strategy to better identify these young people is mental health screening in schools. Despite a growing literature on the benefits of school-based screening, it remains a relatively uncommon practice and little is known about the practices of those schools that do screen. Moreover, the barriers that prevent schools from screening are not well understood. This study reports on the perceptions of school psychologists about universal mental health screening in schools regarding the prevalence of screening; the practices within schools that do screen; and the perceived barriers to implementing screening. Results indicated that screening remains uncommon, with only 14.8% of school psychologists working in schools that screened in the previous 12 months. The most significant barriers to screening related to being adequately resourced to implement programs, and particularly concerns about how to follow-up students identified as being at-risk. Despite this, school psychologists endorse the potential benefit of screening and report being likely to run screening programs if perceived barriers could be reduced.