In this study, 25 oil samples from different reservoir horizons in the Iranian oil fields located in the Persian Gulf were subjected to experimental analyses in order to determine carbon isotope signatures, API gravity, sulfur content and Ni/V ratio. Gas Chromatography and gas chromatography- Mass spectrometry techniques were used to identify and investigate characteristic biomarkers or fingerprints representative of origin, depositional environment, maturity and geological age. Based on distinct physical properties and representative biomarkers, the oil samples were divided into three major families including A, B and C in four different areas. The family A is characterized by carbonate source rocks. The families B and C are assigned to shaly-carbonate and clastic source rocks respectively. The family A is divided into two sub-families including a1 and a2. The sub-family a1 is related to the late Paleozoic to Mesozoic (Lower Jurassic) time interval, and the sub-family a2 is assigned to the source rocks formed during Paleozoic. The family B is divided into three sub-families namely b1 (Late Jurassic- Miocene), b2 (Late Paleozoic- Mesozoic (Lower Jurassic), and b3 (younger than Cretaceous). Moreover, the family C is divided into c1 (Late Paleozoic- Mesozoic: Lower Jurassic), and c2 (younger than Cretaceous) sub-families. This study indicates that petroleum systems in the study area show close similarities with that of the dominant petroleum systems in the neighboring countries; thus, it can be inferred that petroleum systems in this study share many common features by the petroleum systems active the in the Persian Gulf region.