Investigation on the use of diamondoids to assess the extent of thermal maturity, depositional environment, and origin of Niger Delta source rocks was carried out.This was done to evaluate the significant of diamondoids in petroleum exploration in the basin.Pulverized rock samples selected from four Niger Delta oil wells, were extracted with Soxhlet extraction technique.The biomarkers content of saturated hydrocarbons fraction was assayed by gas chromatog.-mass spectrometry (GC-MS) while the diamondoids content was analyzed using GC-MS-MS.The distribution of saturated hydrocarbons; n-alkanes, pristane, pyhtane, steranes, and terpanes revealed that samples from well AW were sourced from mixed terrestrial/marine organic matter while samples from wells OP, GB, and OT were sourced largely from terrestrial organic matter origin.The Pr/Ph ratio values indicated that the organic matter of wells AW and OP samples were deposited under suboxic conditions while those of wells GB and OT were deposited under anoxic conditions.Hopane and sterane thermal maturity geochem. parameters showed that the organic matter in source rocks from the four wells are thermally mature.Diamondoids source parameters indicated that well AW source rock samples had mixed marine/terrestrial organic matter input, while samples from wells OP, GB, OT were sourced from terrestrial organic matter, which is in perfect agreement with the results of other source geochem. parameters, thus indicating that diamondoids are good tools in determining the origin of petroleum.Diamondoid maturity parameters showed that all the samples from the four wells are thermally mature with maturity level ranging from early to main oil window.This study revealed that diamondoids can be used to evaluate petroleum occurrence in the study area or any other sedimentary basins.