In-service trainings for teachers provide information to influence teacher practice within the complex, dynamic environment of the classroom. Transfer of learning, the ability to use previously learned information in a novel setting or time, is necessary for generalization to actual practice (Sork and Caffarella, 1998). Teachers report that current in-service programs are insufficient to meet their needs (Joyce and Showers, 1993). Studies have shown that transfer of learning is not achieved for the majority of teachers (Jacob & McGovern, 2015; Awoniyi, Griego, & Morgan, 2002) and more effective methods of delivery should be considered (Davies & Ray, 2014). Adult Learning Theory as proposed by Malcolm Knowles was explored as a possible solution. The aim of this study was to determine if an in-service based in Adult Learning Theory could influence transfer of learning for teachers. In this post-test only design, middle school teachers at four New Hampshire middle schools were randomized either an in-service experience based in Adult Learning Theory or in a lecture format. Learning assessments including a post education assessment and ranking of activities followed the training. No statistically significant difference was found between the means of the assessment scores of the two groups. The results of the current study demonstrated that Adult Learning Theory did not impact transfer of learning in the short term for a 90-minute in-service. This investigation provides insight into challenges with the application of Adult Learning Theory to teacher in-service as it stands today and suggests alternatives for how in-service training may better promote transfer of learning. [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://www.proquest.com.bibliotheek.ehb.be/en-US/products/dissertations/individuals.shtml.]