Biologists, lay adults, and children alike value causalexplanations of how biological entities work. Despite this,elementary school science education has historically lackedmechanistic content. In line with recent science educationstandards, we investigated the effects of mechanistic learninggoals on understanding of an in-depth lesson about how theheart works. Children ages 6 to 11 who were given mechanistic learning goals performed better on knowledge assessments of the heart lesson and enjoyed their learning goal more than children who were given a relatively superficial learning goal—to focus on labels. Thus, learning goals orienting children towards mechanistic content during lessons enhance science learning and enjoyment.