Abstract The Gulf was contaminated with a large quantity of crude oil during the Gulf War in 1991. Some of the oil beached on the shorelines of the Northwest coast of Qatar. It was discovered, during a sampling campaign in 2015, that the shorelines were contaminated with both fresh oil and heavily weathered oil that could be originating from the Gulf War. A total of 38 oil spill samples were collected during two sampling campaigns and analysed with gas chromatography - mass spectrometry (GC–MS). The chemical fingerprints of petroleum biomarkers and C0-C4 alkyl-substituted polycyclic aromatic compounds for these spill samples were compared to those of more than 250 crude oils from around the world applying the CHEMSIC method (chemometric analysis of selected ion chromatograms). The weathering degree varied significantly between samples, and relatively unweathered oil from the Gulf War oil spill is still found in the Al Zubarah area together with oil from more recent spills. The spill samples were found to originate from at least two sources with most resemblance to oils from Kuwait and Saudi Arabia.