This study was performed to examine and compare the esophagus and stomach histomorphological and histochemical characteristics during adulthood to clarify micromorphological alterations. In addition to the importance of this animal species as a model in many scientific experiments and due to some of its unique anatomical and physiological features. It also supports further studies on vital processes of the digestive system, such as food processing and absorption. To conduct such a project, ten heathy adult guinea pigs at 2 months age and weighing 461.8±8.3g were gathered from the public spinning market. The animals were euthanized and dissected, then the organs were topographically investigated in situ, and samples were collected from the ten animals and was kept in 10% neutral buffered formalin for routine histological procedures. The esophagus is a musculo – membranous tube structure extended from the pharynx to the stomach, measured about 10.54±0.14 cm in length and 0.35±0.01 g in weight, and segmented according to its position in the body into three sections: the cervical, thoracic, and abdominal. The stomach is a simple unilocular transverse grayish white sac-like structure of the digestive system; it connects the esophagus to the intestine; its mean length was 4.39±0.11 cm; its capacity was 17.01±0.22 ml; and its weight was 7.07±0.05 gm. It lacks an outward demarcation-limiting ridge between its divisions and appears relatively smooth. Histologically, the esophagus is devoid of glands, while the stomach's three interior sections are dotted with glands, and both organs consist of the same four basic histological layers.