As mean global temperatures continue to rise, regional seawater temperature measurements have revealed that some geographic areas are warming faster than others. One region that is experiencing particularly rapid warming is the western Antarctic Peninsula. Previous studies investigating direct effects of warming on Antarctic marine invertebrates have established that small increases in temperature can have significant impacts on aspects of behavior, physiology, and growth rates in these largely stenothermal organisms. To investigate how warming may impact feeding preferences of an ecologically important mesograzer on macroalgae of the Antarctic Peninsula, we examined the impacts of exposure to acute elevated temperature on the ecologically important omnivorous amphipod Gondogeneiea antarctica (Chevreux) at Palmer Station, Antarctica (64°46′S, 64°03′W) in April–May 2011. Amphipods were exposed to 1.5 °C (mean monthly upper summer temperature) or 3.5 °C (representative of current transient summer temperature peaks and projected mean for 2100) for a 24 h period. These amphipods were then used in choice-feeding assays with artificial food containing chemical extracts from six species of sympatric macroalgae known to produce feeding deterrents. We found that during acute exposure to elevated temperature (+2.0 °C), amphipods lost their feeding preferences in assays with artificial foods containing lipophilic (one macroalga), hydrophilic (three macroalgae), or combined lipophilic/hydrophilic (one macroalga) extracts. Our findings suggest that increased frequency in transient peaks and longer-term upward trends in ambient summer seawater temperature have the potential to alter feeding preferences in a common mesograzer that could influence macroalgal communities that dominate benthic communities along the western Antarctic Peninsula.