Background: Mental health problems are common among youth in high school, and school counselors play a key role in the provision of school-based mental health care. However, school counselors occupy a multispecialist position that makes it difficult for them to provide care to all of those who are in need in a timely manner. A Web-based mental health service that offers screening, psychological therapy, and monitoring may help counselors manage time and provide additional oversight to students. However, for such a model to be implemented successfully, school counselors' attitudes toward Web-based resources and services need to be measured. Objective: This study aimed to examine the acceptability of a proposed Web-based mental health service, the feasibility of providing this type of service in the school context, and the barriers and facilitators to implementation as perceived by school counselors in New South Wales (NSW), Australia. Methods: This study utilized an online cross-sectional survey to measure school counselors' perspectives. Results: A total of 145 school counselors completed the survey. Overall, 82.1% (119/145) thought that the proposed service would be helpful to students. One-third reported that they would recommend the proposed model, with the remaining reporting potential concerns. Years of experience was the only background factor associated with a higher level of comfort with the proposed service (P=.048). Personal beliefs, knowledge and awareness, Internet accessibility, privacy, and confidentiality were found to influence, both positively and negatively, the likelihood of school counselors implementing a Web-based school mental health service. Conclusions: The findings of this study confirmed that greater support and resources are needed to facilitate what is already a challenging and emotionally demanding role for school counselors. Although the school counselors in this study were open to the proposed service model, successful implementation will require that the issues outlined are carefully addressed. [ABSTRACT FROM AUTHOR]