While The Chronicles of Narnia do not describe the Calormene religion in great detail, they offer a number of clues that give insight into the belief system:
- Tirian described his childhood visit to Tashbaan and noted that the Temple of Tash contained a statue of the god.
- Tash's name was often mentioned in conjunction with epithets like "the inexorable" and "the irresistible." 
- The Tisroc, the Calormene head of state, claimed descent from Tash, and Aravis Tarkeena mentioned that her father's family was "descended in a right line from the god Tash".
- Aravis described a ritual performed by Calormeme women in preparation of marriage: the bride-to-be would go into the wilderness and perform three days of ceremonial sacrifices to Zardeenah, as an indication that they were leaving the goddess' service when they married.
- It was mentioned that the calendar of the religion included an Autumn Feast (the time Aslan decreed that Prince Rabadash must stand in the Temple of Tash to be cured of his donkey's form).
Based on this information, the Calormene religion seems to be a formalized belief system, with specific rules and rituals. Tirian's story illustrates two key points; that the religion had established centers of worship (at least within Tashbann), and that it made use of idols (at least of Tash).
Calormene religion also seemed to be tied into the structure of the government, though the county was not a "theocracy" in the strictest sense of the word. The Tisrocs claimed descent from Tash, and this ties into real-world concepts such as the Divine Right of Kings and the Mandate of Heaven, where political authority was, in some way, connected with religious/spiritual status.
It has been widely speculated that C. S. Lewis was comparing the Calormene religion to Islam (though its followers, Muslims, are strict monotheists, not polytheists). Lewis, though, praised aspects of Islam in some of his works, and the name "Aslan" is a Turkish word (meaning lion). Specifically, Calormene religion resembles the medieval European misconceptions of Islam as a polytheistic religion.