The objective of this study was to investigate structural changes in the penile corpus cavernosum of prepubertal chronically stressed rats. Eight Wistar rats were assigned into the stress group (SG) and were submitted to 2 hours of tube restraint daily, from the fourth to the ninth week of life. Another 7 rats were used as the control group (CG). All animals were weighed weekly. At day 64, animals were sacrificed by anesthetic overdose, blood was collected for testosterone concentration by radioimmunoassay, and penis and adrenal were collected. Adrenal mass index and testosterone serum levels were used to assess the efficacy of the stress stimulus. The surface density of connective tissue and smooth muscle fibers of corpus cavernosum were measured on Masson trichromic-stained slices. Picrosirius red-stained slices were assessed under polarized light for different types of collagen. The Student's t test was applied for mean comparisons, with P < .05 considered significant. Testosterone serum concentrations decreased and adrenal mass index increased, confirming the effectiveness of the stress protocol. Smooth muscle fibers of corpus cavernosum decreased from 14.07% (CG) to 8.98% (SG) (P = .02), and connective tissue increased from 53.66% (CG) to 64.47% (SG) (P = .01). Also, there was a higher level of type I collagen in the SG animals compared with the CG. Stress stimuli induced structural changes in the corpus cavernosum of rats suggestive of penile fibrosis, which may play a role in erection dysfunction.