College undergraduate students traditionally reduce their engagement in physical activity during college, despite the negative health consequences sedentary behavior has been linked to. Mobile health (mhealth) interventions have become increasingly popular for health behavior change, however theoretically based interventions via mhealth are often unclear or vague in how they are developed and how successfully the theory is incorporated into these interventions. This current project explores whether Self-Determination-Theory (SDT) can be successfully translated into a text messaging program designed to increase physical activity in college students. 359 undergraduates participated in a three-phase study to investigate whether SDT needs can be successfully fulfilled by messages of 140 characters or less. 65 theory-based messages were compared to 60 control messages on the degree to which they successfully elicit feelings of relatedness, autonomy, and competence. Results suggest that messages created to fulfil the three needs posited by SDT did so successfully, however in aggregate these messages did not do so more than the control messages did. These results suggest that it is possible for SDT to be translated to text messages, however more research is needed to understand how exactly the messages may be doing so if a group of inspirational messages yielded similar results. Regardless, this project adds to the literature because it is one of the first to detail the process of theory translated into an mhealth intervention.