Phthalides, and their corresponding dihydro and tetrahydro analogues, are components of several genera of the plant family Apiaceae. These taxa have been reported as exhibiting a wide range of bioactivities against experimental models of several illnesses and physiological conditions, including microbial and viral infections, stroke, tuberculosis, and vasoconstriction. Many of these genera are purported to possess medicinal values, and of these several are considered to be traditional herbal medicines. This review provides an overview of the methods of investigation, the structural diversity, and the bioactivity of phthalides, dihydrophthalides, tetrahydrophthalides, and dimers from plants in the Apiaceae.