An understanding of human embryology is essential for students to better understand the subjects of human anatomy and physiology. However, human embryology is a challenging subject for many, since they must learn how anatomic structures and physiological processes develop over a period of time. Embryology texts typically use static, two-dimensional images to illustrate the dynamic three-dimensional developmental processes, making it difficult for a student to understand spatial relationships and sequential steps. To help students conceptualize these series of complex dynamic developmental events that occur over time, two of the authors and a graphic artist developed six web-based cardiovascular embryology animations and housed them on an Indiana University website. This research study examines knowledge gains and user satisfaction of students, faculty, and laypeople around the world who accessed these six website animations. Data collection spanned 6 yr, and pretest/posttest assessments (ranging from 4 to 7 multiple-choice questions each) were used to determine immediate knowledge gains of cardiovascular embryology. The total number of completed pretest/posttest assessments ranged from 555 to 1,449 per animation. The number of correct posttest scores was significantly improved over matched pretest scores (confidence interval range 1.3–3.2, depending on the animation, P < 0.001), suggesting the animations are useful for embryology learning (at least in the short term). Demographic and user satisfaction information was gathered with an anonymous survey at the end of each animation. Survey data from all animations indicated participants found the animations easy to use and very effective for their learning. This research highlights the positive impacts of web-based animations on learning complicated events of cardiovascular embryology.