In Malaysia, Islam is the religion of the state, although other religions may be practised in peace and harmony. Having inherited the English common law tradition at its independence in 1957, Malaysia is neither a secular state nor an Islamic theocracy. As a matter of fact, the Malaysian Constitution has brought Islamic law under the legislative powers of the federal States. Historical developments have thus led to the existence of two sets of law: common law and shari'ah law. Legal pluralism in Malaysia applies foremost to personal status, but also to some aspects of criminal law. The shari'ah as well as legal pluralism seem to question the rule of law in Malaysia. This two-fold aspect of the rule of law will be analysed in this article. The formal definition of the ‘rule of law’ implies the respect for the hierarchical principle and the Constitution’s supremacy. It will be explained to what extent legal pluralism in Malaysia is challenging the supremacy of the Constitution. Nevertheless, the hierarchical principle is not a goal in itself, and the material definition of the ‘rule of law’ will also be discussed. The second part of this article will focus on potential human rights issues that are implied by the notion of legal pluralism and by shari'ah law in Malaysia.