Background Aspartame is the most popular artificial sweetener consumed by many individuals worldwide. Yet, there is still a debate on its consumption as an alternative to sugar. Further studies are warranted to assess the effects of aspartame on pancreas morphodynamics. Aim of the study The present study aimed to evaluate the effects of chronic aspartame administration on the histological structure of rat pancreas. Materials and methods Twenty male albino rats aged 3 months were divided into two equal groups: a control group (group I) and an experimental group (group II), which included rats that received 250 mg/kg/day aspartame once daily for 6 months. The pancreatic tails were processed for light and electron microscopy. The pancreatic islets were evaluated by immunohistochemical stain for the identification of insulin-secreting β cells. Results In group II, binucleated acinar cells, prominent nucleoli, and a relative decrease in secretory granules were observed. Some islet cells showed an acidophilic granular cytoplasm and deeply stained nuclei. A strong positive immunoreaction for insulin was observed in β cells. Ultrastructurally, acinar cells showed euchromatic nuclei with multiple nucleoli. The proliferation and dilatation of rough endoplasmic reticulum had occurred with disturbed cell polarity. Secretory granules were deficient in most acinar cells. β Cells showed an apparent increase in the amount of secretory granules, especially immature ones, and a variable degree of vacuolation. Conclusion Chronic administration of aspartame to adult rats could exert a hyperstimulatory effect on pancreatic acinar and β cells, leading to the risk of development of pancreatitis and/or diabetes