Not all pesto is vegetarian, because some pesto recipes and most store-bought pesto sauces will include animal-rennet-based parmesan (and animal rennet is taken from calves' stomachs). But I was able to find rennet free parmesan and ricotta at the grocery store, so this recipe is completely veggie-friendly! (Just look at the ingredients list of the cheese you buy to find an animal-rennet-free cheese for this recipe!) You can also find some vegetarian friendly store bought pesto - Trader Joe's and Sprouts Organic grocery stores both carry a veggie-friendly and vegan pesto.