An interdisciplinary undergraduate atmospheric science modeling course was cotaught at a midsize public university by three professors from atmospheric science, statistics, and design using a blended learning approach. The in-class portion of the course taught upper-level students numerical weather prediction modeling and statistical evaluation methods. Online modules were used to teach data visualization techniques and three foundational design principles upon which their efficacy depends: legibility, visual hierarchy, and appropriate use of color. Geoscience students need data visualization skills to prepare for careers in government, industry, and research that increasingly require work with big data and communication with diverse collaborators and audiences. This article focuses on the instructional approach for the visualization component of the course--specifically, the three teaching innovations used: online modules, an interdisciplinary teaching team, and design-focused data visualization instruction. Although course enrollment was low at four students, several valuable lessons were learned that can improve the teaching of visualization in geoscience courses, including the utility of structuring visualization instruction around two separate but complementary visualization skills: visualization for analysis and visualization for sharing knowledge. Evaluation of students' visualization work at the conclusion of the course demonstrated improvement in the foundational design principles as well as improved ability to select appropriate visualization strategies for different situations. The methods used to assess these improvements are presented alongside illustrative examples of student work. Pre- and postcourse surveys indicate the students felt more confident in creating data visualizations upon completion of the course, and qualitative assessments of student work confirm increased application of foundational design principles in visualizations created by the students. The authors argue that teaching visualization as an online supplement to other geoscience instruction is a potentially replicable model for improving students' learning about visualization. This is especially true when such instruction relies on open-source programs and materials and leverages interdisciplinary expertise in course design.