Some ten sanctuaries have been identified in Mari, although many more are mentioned in texts from City II and City III. The city was a major religious centre, dominated by its high terraces: the foundation deposits found in sanctuaries, and the votive inscriptions engraved on some statuettes have made it possible to identify some of the deities worshipped by the Mariotes of City II.
Nothing is known about the sanctuaries of City I. The best-known date from City II. Several sanctuaries have been found south and north of the ”Massif Rouge", including the sanctuary of the Lord of the Land (LUGAL DINGIR KALAM). To the south of this sanctuary, three other temples have been excavated, including the temple known as "Ninizaza" where a form of the goddess Inanna was worshipped. A major sanctuary has been found in the so-called ”Presargonic palace” (City II), although it is not known who it was dedicated to. Away from the monumental centre, the temple of Ishtar stood along the inner rampart, north of a city gate.
Major changes were made to the monumental centre during the construction of City III. A new complex was built to the west of the “Massif Rouge" combining a massive terrace and an adjoining sanctuary, known as the temple of the Lions which replaced the former temple of the Lord of the Land which was razed to the ground. New sanctuaries were built to the south of this complex, including one to the mother goddess Ninhursag and another to the god Shamash, which was given a monumental terrace during the Amorite period.
Little is known about the rituals themselves. Processional aisles, libation bowls and altars with small cupules have been easy to identify. Peculiar to Mari are small elongated libation bowls, called ">barcasses", placed at the base of walls. Placed at different stages, these installations guided worshippers through rituals, offerings and libations to the deities but also to the many statues placed in the sanctuaries of City II. The statues of divinities, often made from precious materials, have disappeared. A stela possibly depicting a goddess was discovered in 1997.
Mari is also known for the cult of erected stones and several baetyls have been discovered on the site: they are the expression of an early tradition of aniconism in a world otherwise saturated with images.
Late texts describe extremely complex ceremonies, including the ritual ofIshtar, which involved orchestras and singing. One of the major festivals was the ritual of the dead, the kispum, to honour deceased members of the royal family and other families.
The art of divination is already attested in the Presargonic era and grew in importance in the early 2nd millennium. It was practiced mainly for the king, who used it before taking major decisions, according to the royal archives of Mari. There were several ways to predict the future, and some were used in parallel: