OBJECTIVE: To evaluate the natural healing of the rat diaphragm that suffered an extensive right penetrating injury.METHODS: Animals were submitted to an extensive penetrating injury in right diaphragm. The sample consisted of 40 animals. The variables studied were initial weight, weight 21 days after surgery; healing of the diaphragm, non-healing of the diaphragm, and herniated abdominal contents into the chest.RESULTS: Ten animals were used as controls for weight and 30 animals were operated. Two animals died during the experiment, so 28 animals formed the operated group; healing of the diaphragm occurred in 15 animals (54%), 11 other animals showed diaphragmatic hernia (39%) and in two we observed only diaphragmatic injury without hernia (7%). Among the herniated organs, the liver was found in 100% of animals, followed by the omentum in 77%, small bowel in 62%, colon in 46%, stomach in 31% and spleen in 15%. The control group and the diaphragmatic healing subgroup showed increased weight since the beginning of the study and the 21 days after surgery (p <0.001). The unhealed group showed no change in weight (p = 0.228).CONCLUSION: there is a predominance of spontaneous healing in the right diaphragm; animals in which there was no healing of the diaphragm did not gain weight, and the liver was the organ present in 100% the diaphragmatic surface in all rats with healed diaphragm or not.