Tom yum is characterized by its distinct hot and sour flavors, with fragrant herbs generously used. The basic broth is made of stock and fresh ingredients such as lemon grass, kaffir lime leaves, galangal, limejuice, fish sauce and crushed chili peppers.

Tom yum is usually made with prawns (tom yum goong or tom yum kung), chicken (tom yum kai), fish (tom yum pa in Laotian and tom yum pla in Thai), or mixed seafood (tom yum thale or tom yum po taek) and mushrooms - usually straw mushrooms or oyster mushrooms. The soup is often topped with generous sprinkling of fresh chopped cilantro (coriander leaves).