A meta-analysis of 26 primary studies, yielding 76 pair-wise comparisons of dynamic and static visualizations, reveals a medium-sized overall advantage of instructional animations over static pictures. The mean weighted effect size on learning outcome is d = 0.37 (95% CI 0.25-0.49). Moderator analyses indicate even more substantial effect sizes when the animation is representational rather than decorational (d = 0.40, 95% CI 0.26-0.53), when the animation is highly realistic, e.g., video-based (d = 0.76, 95% CI 0.39-1.13), and/or when procedural-motor knowledge is to be acquired (d = 1.06, 95% CI 0.72-1.40). The results are in line with contemporary theories of cognitive load and multimedia learning, and they have practical implications for instructional design.