In the search for models that can reproduce human pathophysiological conditions and/or provide the assessment of new drugs, research using animals are growing, resulting in increased demand for animals. Care in the creation and use of such animals are essential, aiming at maintaining animal welfare. Against this backdrop, it is important to have knowledge about the likely environmental impacts that the maintenance of these animals may generate. Thus, this study aimed to model the environmental performance for the maintenance of small animals using the Life Cycle Assessment methodology (LCA). For this there were two simulated physical spaces (SPS), comprising 375 rats and 625 mice. To obtain the results, the steps of an LCA were followed according to the methodology defined by the ISO 14040 standard. Our results demonstrate that in LCA for rats, it is produced about 329 kg of CO2 equiva¬lent and 62.10-3 kg of MP2,5 , and in LCA for mice, it is produced about 87.93 kg of CO2 equivalent and 19.10-3 kg of MP2,5. Several studies correlate high levels of CO2 equivalent and MP2,5 in the atmosphere to cardiorespiratory diseases, demonstrating that the environmental impacts caused by maintenance and laboratory animal disposal are significant. Research with animals is a reality and without them the biomedical sciences in general would not have reached the current progress, however, should follow the principle of the “3Rs” (Reduction, Refinement and Replacement). It must consider the environmental impacts that maintaining these animals may generate, reinforcing the idea of responsible use.