Sexual health text message services are becoming an increasingly popular way to provide adolescents with accurate sexual health information, but promotion of such services is often limited. This study uses three quantitative methods (service use data, a text message-based questionnaire, and an in-school online survey) to assess the effectiveness of an in-school social marketing campaign promoting a sexual health text message service that connects teens directly with a health educator. The 3-month campaign was associated with increased service use, but use was still relatively low. Follow-up qualitative work that included focus groups and interviews found a number of barriers to use. Teens indicated they did not have sexual health questions, did not think of the service, or were unsure how to use it. Teens also brought up additional barriers such as concern over parents seeing the messages. Implications for text message service providers and health educators are discussed.