Phylogenetic trees are used throughout biology to represent evolutionary relationships and communicate ideas about evolutionary processes. Dedicated instruction in how to read and interpret phylogenetic trees (i.e., tree thinking) is necessary for students to be able to access this information. There are many cognitive barriers to mastering tree-thinking skills, and for some students, such as students who are blind or low-vision, there are physical barriers. We used a Universal Design for Learning (UDL) approach to increase the accessibility of the Great Clade Race, an effective activity for teaching tree-thinking skills. Here we provide an example of how applying a UDL approach reduced not only known barriers, but also barriers that were undetected until they were removed, providing benefits to all students.