Treatment providers seek low-cost, high-impact means of engaging clients in care with the aim to enhance treatment delivery and outcomes. With improvements to mobile technology making cell phone accessibility and usage rates high across all socio-economic levels, text messaging is becoming more frequently utilized as a means of promoting provider-client communication. Numerous studies have demonstrated the efficacy of text message interventions in healthcare; touting a wide variety of achievements including increased treatment session attendance, improved medication compliance, enhanced client satisfaction, decreased symptomology, reduced substance use, and a reduction in rates of recidivism. While text messaging is being utilized as an intervention by a growing number of healthcare providers, the literature is lacking related to the linguistic composition of text messages used in treatment. To extend this knowledge base, text message communications utilized in the treatment of mental health and substance use disorders were collected from previously published research and added to a corpus for analysis. Linguistic Inquiry and Word Count (LIWC) software was utilized to explore writer communication style and use of terminology thought to enhance client engagement. Results demonstrated statistical significance when compared to national blog norms derived from Twitter. Text messages for both mental health and substance use disorder treatment had high levels of Clout, demonstrating the text writer’s confidence and expertise. However, Authenticity, which indicates communication that is both honest and personal, was found to be low in all messages. The Emotional Tone of mental health text messages was positive, while substance use disorder messaging demonstrated a neutral tone. Both sets of text messages had a higher rate of Biological terms used than expected while Informal terminology was used at a much lesser rate than national norms. Substance use disorder text messages demonstrated more frequent use of leisure terms, nearly three times the national norm.