In this study, the instructional effectiveness of the planetarium in astronomy education was explored through a meta-analysis of 19 studies. This analysis resulted in a heterogeneous distribution of 24 effect sizes with a mean of +0.28, p .05. The variability in this distribution was not fully explained under a fixed effect model. As a result, a random effects model was applied. However, a large random effect variance component indicated that study differences were indeed systematic. The findings of this meta-analysis showed that the planetarium has been an effective astronomical teaching tool.