This paper aims to verify the effects of severe protein malnutrition over the intestinal ascending colon morphometrics in adult rats. 12 rats (90 days old) were divided into 2 groups: control (n = 5) and malnutritioned (n = 7). In the following 90 days, the rats of the control group received a 24% protein chow as the malnourished group received 4% protein chow. The animals were submitted to euthanasia according to the anesthetic protocol. Colon segments were collected and submitted to routine histological processing. The cuts were stained with HE and histochemical techniques for mucines. The morphometric analyses showed the sustenance of the whole wall and muscle tunic thickness, as well as the reduction of the thickness of the mucosa tunic, the amount of goblet cells, the depth of the crypt and the height of the enterocytes as well as their nucleus on malnutritioned animals. The data suggest that protein malnutrition causes alterations on adult rat ascending colon intestinal morphometrics, especially in tissues which present a high level of cell turnover such as the mucosa tunic and consequently their structures such as the enterocytes, goblet cells, and crypts.