Reductions in laboratory hours have increased the popularity of commercial anatomy e-learning tools. It is critical to understand how the functionality of such tools can influence the mental effort required during the learning process, also known as cognitive load. Using dual-task methodology, two anatomical e-learning tools were examined to determine the effect of their design on cognitive load during two joint learning exercises. A.D.A.M. Interactive Anatomy is a simplistic, two-dimensional tool that presents like a textbook, whereas Netter's 3D Interactive Anatomy has a more complex three-dimensional usability that allows structures to be rotated. It was hypothesized that longer reaction times on an observation task would be associated with the more complex anatomical software (Netter's 3D Interactive Anatomy), indicating a higher cognitive load imposed by the anatomy software, which would result in lower post-test scores. Undergraduate anatomy students from Western University, Canada (n = 70) were assessed using a baseline knowledge test, Stroop observation task response times (a measure of cognitive load), mental rotation test scores, and an anatomy post-test. Results showed that reaction times and post-test outcomes were similar for both tools, whereas mental rotation test scores were positively correlated with post-test values when students used Netter's 3D Interactive Anatomy (P = 0.007), but not when they used A.D.A.M. Interactive Anatomy. This suggests that a simple e-learning tool, such as A.D.A.M. Interactive Anatomy, is as effective as more complicated tools, such as Netter's 3D Interactive Anatomy, and does not academically disadvantage those with poor spatial ability. Anat Sci Educ 9: 378-390. © 2015 American Association of Anatomists.