Noise pollution is an unprecedented evolutionary pressure on wild animals that can lead to alteration of stress hormone levels and changes in foraging behavior. Both corticosterone and feeding behavior can have direct effects on gut bacteria, as well as indirect effects through changes in gut physiology. Therefore, we hypothesized that exposure to noise will alter gut microbial communities via indirect effects on stress hormones and foraging behaviors. We exposed captive white-crowned sparrows to city-like noise and measured each individuals’ corticosterone level, food intake and gut microbial diversity at the end of four treatments (acclimation, noise, recovery, and control) using a balanced repeated measures design. We found evidence to support our prediction for a causal, positive relationship between noise exposure and gut microbiota. We also found evidence that noise acts to increase corticosterone and decrease food intake. However, noise appeared to act directly on the gut microbiome or, more likely, through an unmeasured variable, rather than through indirect effects via corticosterone and food intake. Our results help to explain previous findings that urban, free-living white-crowned sparrows have higher bacterial richness than rural sparrows. Our findings also add to a growing body of research indicating noise exposure affects stress hormone levels and foraging behaviors. Altogether, our study indicates that noise affects plasma corticosterone, feeding behavior, and the gut microbiome in a songbird and raises new questions as to the mechanism linking noise exposure to gut microbial diversity.