This research experimentally manipulated the social presence cues in instructor's messages to students. The context was an online professional development one-credit course with one-to-one mentoring of students. Additionally, student learning intentions and levels of trust were examined as factors that may mitigate the effects of social presence. Results indicate that social presence affects the learner's interactions and perception of the instructor but has no effect on perceived learning, satisfaction, engagement, or the quality of their final course product. These findings suggest social presence is a correlational rather than a causal variable associated with student learning. Exploratory analyses suggest that trust and learning intentions are potentially important factors impacting student perceptions of the learning environment and performance in the course respectively.