Environmental toxicants and stress influence the health and behavior of people from different parts of the world. In the present study, aggressive behavior was evaluated in rats exposed to cadmium (Cd) for four weeks and subjected to immobilization stress (IS) based on the resident/intruder paradigm. Latency to the first bite (LB), total number of attacks (NA), total duration of attack manifestations (DAM), and a composite aggression score (CAS) were used to assess aggressiveness. Cadmium concentrations in the blood and the brain were determined. We observed that the parameters of aggressiveness were not altered by either Cd or IS when administered separately. However, animals exposed to Cd+IS had increased NA, DAM, and CAS. Cadmium was detected in the blood and the brain after treatment and Cd+IS exposure modified Cd distribution in these tissues. These results suggest that exposure to low levels of Cd associated with stress may lead to increased aggressiveness in rats.