Laurel cherry (Prunus laurocerasus L.), an evergreen tree from Rosaceae family, is used as a folk medicine for various medical purposes and against diabetes as well in Northern Anatolia. The present study was performed to evaluate in-vivo hypoglycaemic and antidiabetic activities of P. laurocerasus. Hypoglycaemic effect of ethanol extracts of the fruit and seeds were tested on normoglycaemic, glucose loaded and streptozotocin induced diabetic rats. The extracts were given orally to rats and blood glucose levels were determined according to the glucose oxidase method. The results indicated that seed extract showed 20% inhibition on blood glucose levels on experimental diabetic animals Chemical composition of the bioactive seed extract was analyzed by GC-MS. Oleic, linoleic and palmitic acids were detected as the major components of this extract. Therefore, hypoglycaemic activity of the seeds may be arisen from unsaturated fatty acids.