Aims: Hyperglycaemia leads to impaired mitochondrial respiration in pancreatic islets. The nutrient-sensing mechanistic target of rapamycin complex 1 (mTORC1) pathway is hyperactivated in islets from patients and animals with Type 2 diabetes. We aimed to investigate if inhibition of mTORC1 could restore mitochondrial efficiency in diabetic islets. Methods: We utilised the βV59M mouse model whereby hyperglycaemia/diabetes (>20mmol/l) is initiated via a tamoxifen-inducible KATP channel activating mutation in pancreatic beta cells. mTORC1 signalling was determined by the ratio of phosphorylated (p-S6) and total ribosomal protein S6 (tot-S6) using standard western blotting methods. Following isolation, islets were incubated with/without 10µmol/l S6 kinase inhibitor PF-4708671 (S6Ki) for 48 hours. Oxygen Consumption Rate (OCR) was monitored using the extracellular flux analyser (Seahorse Bioscience, Inc.). Results: mTORC1 signalling is increased in diabetic islets (p-S6/total-S6 ratio: control = 0.36±0.02 vs diabetic = 0.70±0.082 AU, p<0.05; n=6) but incubation with S6Ki reduced this to levels observed in control islets. Diabetic islets displayed an attenuated glucose-stimulated OCR, in comparison to control islets. However, this was significantly improved following incubation with S6Ki (diabetic = 34.45±10.72 vs diabetic+S6Ki 203.94±39.24% increase in OCR above baseline, p<0.001; n=7-8). The ATP-synthase inhibitor, Oligomycin, produces significantly less inhibition of OCR in diabetic islets, compared to control, but this response was restored via mTORC1 inhibition (diabetic = 55.01±9.44 vs diabetic+S6Ki = 240.32±9.71% decrease in OCR, p<0.001; n=7-8). Conclusion: Our results suggest that hyperactivation of mTORC1 signalling is partially responsible for mitochondrial dysfunction in diabetic islets and may be involved in regulating ATP-synthase activity.