The Perhentian complex consists of two series of plutonic rocks, the younger Perhentian granite and the older Perhentian Kecil syenite. They form a reversely zoned complex where the syenitic rock is rimmed by the granitic rock. The former ranges in composition from syenite to monzonite to gabbroic rocks whereas syenogranite dominates in the latter pluton. The syenitic rocks are characterized by an extended composition of lower SiO2 (46 to 66%) compared to the Perhentian granite (>70.9% SiO2). The granitic rocks have significantly low Al2O3, TiO2, Fetot, MnO, MgO, CaO and P2O5, Sr, Ba and V compared to the syenitic rocks. Petrology and geochemical studies indicate that both rocks were crystallines by individual melts probably derived from different sources. It suggests that the syenitic magma was formed by hydrous melting of lower crust probably as a result of underplating by, or intrusion of mantle derived basaltic magmas. The strong enrichment of large ion lithophile elements (Sr and Ba) is probably related to transfer of enriched (hydrous?) fluids from the mantle into the lower crust, and possibly initiated melting to form the syenite. In contrast to the Perhentian Kecil Syenite, the Perhentian Granite has no mafic association. The felsic nature of the Perhentian granite suggests that it may be derived from a SiO2 rich source or may represent a minimum melt, the first melt produced from a solid containing plagioclase-feldspar-quartz.