Chronic hyperglycemia has been implicated in the development of oxidative stress and as a major factor in etiology of secondary complication in diabetes. In the present study, the antidiabetic potential of Phragamenthra incana (P. incana) hot infusion and its possible inhibitory effects on carbohydrate digesting enzymes, promotion of muscle glucose uptake, and the antioxidative potentials in Fe²⁺-induced oxidative stress in hepatic tissue were investigated. The infusion significantly (p < 0.05) scavenged free radicals (DPPH) and displayed favourable ferric reducing antioxidant power (FRAP) with increasing concentrations. It also significantly ameliorated Fe²⁺-induced oxidative stress in hepatic tissues by increasing superoxide dismutase (SOD) and catalase activities and depleting malondialdehyde (MDA) level. The results further showed that the infusion significantly (p < 0.05) inhibited α-amylase and α-glucosidase activity, and enhanced muscle glucose uptake, with and without insulin. Liquid Chromatography–Mass Spectroscopy (LCMS) analysis of the infusion revealed the presence of 2-methoxythiazole; l-cysteine; nicotinic acid; S-methyl-l-cysteine; isoquinoline, 1-methyl-; and 1H-indole-2,3-dione,5-methyl. The results of this study suggest that the observed antidiabetic and antioxidative potentials of P. incana could be attributed to its identified phytochemical constituents, however, this supports folkloric medicinal use of this plant.