This research analyzed the effects of the Marzano Teacher Observation training on the self-efficacy of teacher observers. In this study, seventy-four teacher observers reported their self-efficacy in the areas of evaluating student engagement, evaluating classroom management, and evaluating instructional strategies in pre and post surveys. The results of the surveys were analyzed with a paired samples t-test. This study found that the Marzano Teacher Observation system increases the self-efficacy of teacher observers. This study was delimited to participants of a Marzano Teacher Observation training conducted in the fall of 2014. The findings of this study will inform executive school leaders of the impact Marzano Teacher Observation training has on the self-efficacy of teacher observers.