Climate change will have negative impacts on diverse taxonomic groups, and ectotherms are particularly at risk because their physiology is so closely tied to the environment. For ectotherms, changes in temperature affect metabolism, development, growth, movement, reproduction, and immunity. To better understand the potential for climate change to impact amphibian immune defenses, I compared (a) the development of immune defenses and (b) the impact of exposure to the chytrid fungus Batrachochytrium dendrobatidis (Bd) among juvenile leopard frogs from three latitudes that had developed under simulated current and future climate conditions. Few studies have examined the impact of increased environmental temperatures during larval development on immune defenses that are expressed after metamorphosis. We predicted that exposure to stressful temperatures early in life would result in juvenile frogs with compromised immune defenses. As predicted, frogs raised as larvae under simulated climate change scenarios metamorphosed faster, and at a reduced body size and mass, compared to frogs raised under their simulated current climates. Effects of simulated warming on immune parameters and disease development differed among latitudes/populations of origin: frogs from our middle latitude were less likely to become infected with Bd as juvenile frogs if they had developed as larvae under simulated future climate scenarios, and frogs from our highest and lowest latitudes that developed as larvae under simulated warming had underdeveloped antimicrobial peptides. In some populations we also found differences in immune cell (white blood cells and/or thymocytes) counts in juvenile frogs that developed as larvae under different climate scenarios.