Mesozoic source rocks and crude oils from the Besikli oil field, Adiyaman, Turkey, havebeen characterized by a variety of organic geochemical techniques. The potential source rocksinvestigated include the Karababa (A, B, and C members) and the Karabogaz formations. TheKarababa-A member and the Karabogaz formation of clayey limestone and limestone areimportant source rocks in the basin. The crude oils examined in this study were obtained fromreservoir formations of the same age throughout the oil field. The source rock screening analysisindicates that the Karababa-A member and the Karabogaz formation have substantialoil-generation potential. The Karababa-B and C members have no source potential because theydo not contain sufficient amount of total organic matter content (0.12–0.24 TOC wt%). Selectedsource rock and oil samples were characterized in detail, and distributions and concentrations (both relative and absolute concentrations, of biomarkers at different oils were examined. Thebiomarker characteristics were combined with other geochemical and geological data to interpretthe sources, depositional environments, and the age of the oils. Oil-source rock correlations weremade between source rocks and crude oils based on qualitative and quantitative biomarkerdistributions. Petrographic descriptions and vitrinite reflectance measurements were used toevaluate petrographic properties of source rocks and maturity levels of the formations. Thesource rocks for the oil from the Karababa-A member and Karabogaz formation are not matureenough and therefore oil should have migrated from the outside of the study area.