Background: Diabetes mellitus is considered one of the 5 principal causes of death in the world and is recognized as a global public health issue because of its multifactorial facets affecting essential biochemical processes in the body. This study investigated the antidiabetic and antidyslipidemic activities of the aqueous extract of Cochlospermum planchonii (C. planchonii) leaves in streptozotocin (STZ)-induced diabetic rats. Methods: Thirty adult female rats (Rattus norvegicus) weighing 153±3.41g were randomized into 6 groups of 5 animals each. STZ-induced diabetic rats were orally administered 50, 100, and 200 mg/kg body weight of the extract, respectively, once a day, and their blood glucose levels as well as variations of diabetes-associated biomarkers including alpha amylase, glucose-6-phosphate dehydrogenase (G6PDH), and lipid profile by the extract were monitored for 21 days. The results were expressed as means±SEMs and compared with repeated measures using SPSS, Data Editor, version 16.0.Results: The aqueous extract of C. planchonii leaves significantly reduced the blood glucose level in a dose-dependent manner, with the highest dose producing a 74.52% reduction after 21 days of administration, which compared significantly (P<0.01) with the control and metformin-treated groups. Similarly, STZ-induced diabetic mediated alterations in the serum lipids were significantly (P<0.01) restored by the extract. In addition, the aqueous extract of C. planchonii leaves significantly attenuated the decrease in the activity of G6PDH and the increase in the activity of α-AMY in the liver of the STZ-induced diabetic rats. Conclusions: Overall, the aqueous extract of C. planchonii leaves could be used to manage diabetes and other related complications.