Will a warmer world be a sicker world? What is it about the New England landscape that supports the proliferation of Lyme disease? How are local wildlife trade and global species invasions contributors to emerging diseases such as the 2003 outbreak of monkey pox virus in the midwestern United States? Undergraduate students explore these and related questions in BIOL 1455 Planetary Health: global environmental change and emerging infectious disease—a new online asynchronous course at Brown University. Planetary health is gaining traction in the curricula of institutions of higher learning and online asynchronous courses offer the promise of scaling up to make grand challenges education accessible to many. In our new course, we assessed student learning outcomes (LOs) and sentiment towards the health of humans and the planet using a mixed-methods approach. Students demonstrated competency in each of the LOs after course completion as measured in a pre–post assessment scored with a standardized rubric. Student sentiment was analyzed with an immersion–crystallization qualitative analysis to elucidate themes in responses to the assessments. Many themes on the pre-assessment focused on barriers and problems associated with the health of humans and the planet, while themes on the post-assessment centered on more solutions-based thinking. Collectively, these findings indicate that this online asynchronous course successfully educated students about the myriad challenges facing human and planetary health, broadened knowledge of environmental changes (beyond climate change) that impact health, formalized understanding of now common terms such as “emerging infectious diseases”, and bolstered hope by offering solutions and peer community (even when virtual). Future efforts to integrate planetary health into higher education should focus on broadly accessible and scalable courses, full programs of study (i.e., majors/scholarly concentrations), and extension into institutional programs focused on ensuring equity and wellness for all.