Triglycerides of butyric acid compose 3–4% of butter. When butter goes rancid, butyric acid is liberated from the glyceride by hydrolysis. It is one of the fatty acid subgroup called short-chain fatty acids. Butyric acid is a typical carboxylic acid that reacts with bases and affects many metals.
It is found in animal fat and plant oils, bovine milk, breast milk, butter, parmesan cheese, body odor, vomit and as a product of anaerobic fermentation (including in the colon). It has a taste somewhat like butter and an unpleasant odor. Mammals with good scent detection abilities, such as dogs, can detect it at 10 parts per billion, whereas humans can detect it only in concentrations above 10 parts per million. In food manufacturing, it is used as a flavoring agent.
In humans, butyric acid is one of two primary endogenous agonists of human hydroxycarboxylic acid receptor 2 (), a  G protein-coupled receptor.
Butyric acid is present as its octyl ester in parsnip (Pastinaca sativa) and in the seed of the ginkgo tree.