Heart autonomic ganglia are known to play an important role in cardiac rhythm control, protecting against certain arrhythmias due to their parasympathetic activity. Cardiac disorders may arise following starving states during pregnancy; cardiac performance and cardiac fibers have been shown to suffer deleterious effects under starvation. Morphology of these plexuses may suffer interference of extrinsic factors, but data is still lacking about the effects of low protein diet during pregnancy and early postnatal period on subepicardial neuron structure. Two groups of pregnant Wistar rats were submitted to different diets according to its protein content, normal and 5% casein, until 21 days after delivery. The offspring was divided in two groups, D and N, according to their mother´s diet, low and normal protein respectively, and then sacrificed. The atrial neurons were identified by β-nicotinamide adenine dinucleotide (NADH) and adenine dinucleotide phosphate diaphorase (NADPH-d) staining. Profile areas of the nerve cell bodies were measured. NADH staining did not show significant differences between groups but NADPH- d profile areas of nerve cell bodies from group D were smaller than in control group. Ultrastructural changes were observed in group D rats: agglomerated ribosomes, increase in nucleoli density and irregular chromatin.Low-protein diet in rats at early developmental stages interferes in size, and ultrastructure of subepicardial neurons. Even though underfeeding during perinatal period did not produce neuronal death, neuron development is delayed and permanent changes can supervene in long term.