Role of Muhtasib in the Islamic state was deemed to be one of supervision. The Muhtasib acted like a supervisor, an inspector of markets and censor of morals. It was his duty to see that public worship was duly maintained, public order was not disturbed, that traders used correct weights and measures, and sold pure and unadulterated goods. He could restrain teachers whose doctrines were subversive of Islam and prevent immoral books being read in schools. The Muhtasib was also expected to keep a close check on all doctors, surgeons, blood-letters and apothecaries. Speaking generally, he was subordinate to the judge but he could often act on his own initiative whereas the judge could only act when a case was brought to him. But if there was a conflict of evidence, the Muhtasib had to refer the case to the judge.

Among the functions of the Muhtasib, an important role seems to be that of supervising trade and business. This role of the Muhtasib was very important in the Medieval Islamic countries. He had to make sure that public business was being carried out according to the rules laid down by the Islamic Law, Sharia. For instance, the Muhtasib has also been known to have regulated money, public morals, weights and measures, prices, education, students and teachers, traffic flow, public safety and much more. Even the standards of craft of the craftsmen and builders were regulated by the Muhtasib. In eating houses, the Muhtasib could issue a number of orders for health and cleanliness purposes, such as asking food to be kept covered to protect against flies, ordering worn out pots utensils to be replaced etc.

Several manuals for holders of this office exist. These manuals were known as Hisba and were written particularly for the purpose of providing guidance and direction to the Muhtasib in the execution of his duties. The Hisba contained practical advice and instructions on how to manage and marketplace as well as a number of other things that a Muhtasib needed to know. These manuals proved extremely beneficial as they throw much light on the commercial life of the period and it is clear that a conscientious Muhtasib had to know much about the shady side of life if he were to do his duty.

However there are certain restrictions on the exercise of powers by the Muhtasib. If a man drank wine in public, he was asking for trouble. If he got drunk in private, however much the Muhtasib might suspect, he could not violate the privacy of the man`s house and take him in the act. The law was quite reasonable and the role of the Muhtasib was given due significance.