Objective: To profile the secondary metabolites and to evaluate the antidiabetic potential of hydroethanolic leaf extracts of Conocarpus lancifolius. Methods: The various hydroethanolic extracts of Conocarpus lancifolius leaf were prepared by ultrasonication assisted freeze-drying. Total phenolic contents, flavonoid contents, antioxidant activity, α-glucosidase and α-amylase inhibitions of leaf extracts were determined. The metabolite profiling was accomplished by UHPLC-Q-TOF-MS/MS analysis. The antidiabetic assessment of the most potent extract was carried out by measuring the hypoglycemic and hypolipidemic effect in the high fat diet-fed diabetic albino mice. The blood glucose level, haemoglobin, total cholesterol, high-density lipoproteins (HDL) and low-density lipoproteins (LDL) were determined. Results: The 60% ethanolic extract exhibited the highest phenolic and flavonoid contents of (349.39 ± 2.13) mg GAE/g dry extract and (116.95 ± 2.34) mg RE/g dry extracts, respectively, and the highest DPPH scavenging activity with an IC50 value of (32.87 ± 1.11) μg/mL. The IC50 values for α-glucosidase and α-amylase inhibitions were (38.64 ± 0.93) μg/mL and (44.80 ± 1.57) μg/mL, respectively. UHPLC-Q-TOF-MS/MS analysis confirmed the presence of gallic acid, ellagic acid, corilagin, kaempherol-3-O-rutinoside, caffeic acid derivative, isorhamnetin and galloyl derivatives in the 60% ethanolic extract. Plant extract at a dose of 450 mg/kg body weight reduced blood glucose level, total cholesterol, LDL and HDL, and increased haemoglobin in alloxan-induced diabetic mice, Conclusions: Conocarpus lancifolius leaves are proved as a good source of biologically functional metabolites and possess antidiabetic activity which may be further explored to treat diabetes.