Health messaging can be a successful tool in encouraging pro-social behavior, such as bystander intervention in sexual violence situations. This dissertation explored the development of a social media message to encourage bystander intervention among college students using multiple theoretical frameworks: social norms approach and bystander intervention barriers. After the development of these messages, an experiment was conducted to assess the effect of the messages on attitudes, perceived norms, efficacy, intentions to intervene, and intentions to take responsibility as they relate to bystander intervention. The experiment conditions were four: a norms-based condition, a behavior-based condition, a combination condition, and a control condition. The norms-based condition had an effect on perceived norms and intentions to intervene. The combination condition had an effect on intentions to intervene. These results have implications for our current understanding of bystander intervention models and message development to encourage bystander intervention in sexual violence situations among college students. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://bibliotheek.ehb.be:2222/en-US/products/dissertations/individuals.shtml.]