This study investigated the antidiabetic effects of the rind of Nephelium lappaceum extract in a high fat-induced diabetic rat model. Ethanolic N. lappaceum rind extract was prepared and standardised with geraniin using high performance liquid chromatography. Male Sprague Dawley rats were fed on a high fat diet followed by 210 mg kg-1 nicotinamide and 55 mg kg-1 streptozotocin injection to induce type 2 diabetes. The diabetic rats were treated with N. lappaceum rind at concentrations of 500 and 2000 mg for 28 days. Positive control rats were treated with 200 mg metformin. A 41.1 yield of ethanolic extract was obtained from powdered N. lappaceum rind while geraniin present in the extract was quantified to be 33.0?0.2 mg geraniin/g extract. Our study also showed that the diabetic rats treated with 2000 mg N. lappaceum had reduction in blood glucose level and improved insulin levels which were similar to the metformin-treated group. Pancreas histology showed that the group treated with 2000 mg of N. lappaceum had healthy pancreas morphology and the treatment was comparable to the effects observed in the metformin-treated group. In conclusion, N. lappaceum rind extract showed anti-hyperglycaemic activity at a dose of 2000 mg kg-1 without any major toxic effects in high-fat diet induced diabetic rats.