Understanding the mechanisms by which climate change affects food webs is essential for predicting shifts in community structure and ecosystem functioning. Although the impacts of increasing temperatures and changing precipitation patterns on mesocarnivore diets are well documented, the influence of snowfall variation on their trophic interactions remains poorly understood, particularly based on multi-year dietary datasets. This study evaluated how interannual snowfall variation influences mammalian consumption by red foxes and Japanese martens during winter in northern Japan, one of the world’s snowiest regions. Fecal samples were collected over five winters between 2019 and 2024 in and around forested areas of Tsuruoka City, northeastern Japan. Mammalian prey remains identified in fecal samples were classified into three categories: small mammals, lagomorphs, and medium- to large-sized mammals. We evaluated the effects of snowfall variation on mammal consumption using generalized linear models. The results demonstrated that low snowfall significantly increased the consumption of small mammals by mesocarnivores, whereas the consumption of lagomorphs and other mammals was unaffected by snowfall patterns. These findings suggest that mesocarnivores adjust their diet flexibly in response to snowfall changes. A long-term decline in snowfall may increase the predation success of mesocarnivores on small mammals, potentially affecting their population dynamics. Further research is required to elucidate how shifting snow conditions, driven by ongoing climate change, influence mammalian species interactions and their broader impacts on communities and ecosystems.