The aim of this study was to evaluate possible effects of Passiflora edulis flavicarpa (P. flavicarpa) extract on the labeling of blood constituents with (99m)Tc, on the morphology of red blood cells, and on the biodistribution of sodium pertechnetate (sodium (99m)Tc). Male Wistar rats were treated with either P. flavicarpa extract or 0.9% NaCl. After that, radiolabeling of blood constituents, morphological analysis of red blood cells and biodistribution of sodium (99m)Tc was evaluated. Radiolabeling of blood constituents and shape of red blood cells were not modified, but a significant (p<0.05) alteration of the biodistribution of sodium (99m)Tc was observed after treatment with P. flavicarpa extract. Although our results were obtained with animals, they could contribute to reduce the risk of misdiagnosis and/or repetition of the examinations in nuclear medicine.