The subepicardic ganglion capsule of rat is constituted by connective tissue, type I collagen and rare fibers of the elastic system. Undernutrition is associated to defects of the connective tissue as lesions and altered growth. As collagen is the most prevalent protein in all tissues, its presence was evaluated in a proteic undernutrition model (5% casein) in the subepicardic plexus ganglions of pre and post natal rats with 21 and 42 days and after post natal restart of refeeding. Collagen fibers were identified by picrosirius staining with polarization microscopy and transmission electronic microscopy. Elauninic and oxytalanic elastic fibers were not identified by their staining characteristics and fine structural morphology for the coloration of Verhöeff and Resorcina Fuccina with and without previous passage for the oxona. It was not observed, by optical microscopy, differences between the collagen and elastic fibers in the subepicardic ganglion capsule of the studied groups. However morphometric analysis by transmission electronic microscopy showed that the undernourished groups of 21 and 42 days presented difference in the outline area of the collagen fibers in transversal sections. There was an increase in collagen fiber area of group D (21 days) suggesting an acceleration in the development, once the values obtained in that group were similar to the group NN (nurtured of 42 days). With undernutrition up to 42 days there was a decrease in the collagen fiber area in transversal sections. It was not observed recovery in collagen area after refeeding from 21 to 42 days.