A new and sophisticated saffron adulteration method with gardenia was recently discovered in the European saffron market. In this work, an analytical methodology using liquid chromatography-(quadrupole-time of flight)-mass spectrometry has been developed for the detection of the adulteration of saffron samples with gardenia through the determination of geniposide as an adulteration marker. A fused-core C18 column was employed using an isocratic elution with water:acetonitrile (85:15v/v) containing 0.1% formic acid. After optimization of the mass spectrometry conditions, the analytical characteristics related to the determination of geniposide in negative electrospray ionization mode were evaluated. Then, it was possible to detect up to 10ng/mL geniposide after a dilution step of 50-fold of the saffron extract (LOD of 41.7μg of geniposide per gram of sample analysed (i.e up to 0.004%)). The developed LC–MS methodology was applied to the analysis of different authentic and suspicious saffron samples.