This study investigated the effects of Augmented Reality (AR) on learning, cognitive load and spatial abilities. More specifically, it measured learning gains, perceived cognitive load, and the role spatial abilities play with students engaged in an astronomy lesson about lunar phases. Research participants were 182 students from a public university in southeastern United States, and were recruited from psychology research pool. Participants were randomly assigned to two groups: (a) Augmented Reality and Text Astronomy Treatment (ARTAT); and (b) Images and Text Astronomy Treatment (ITAT). Upon entering the experimental classroom, participants were given (a) Paper Folding Test to measure their spatial abilities; (b) the Lunar Phases Concept Inventory (LPCI) pre-test; (c) lesson on Lunar Phases; (d) NASA-TLX to measure participants’ cognitive load; and (e) LPCI post-test. Statistical analysis found (a) no statistical difference for learning gains between the ARTAT and ITAT groups; (b) statistically significant difference for cognitive load; and (c) no significant difference for spatial abilities scores.