Abstract Aggression behavior is among the most efficient means of competition, which achieves dominance of gaining access to resources, and ensures individual survival and reproductive success. The present study was aimed to understand the energy strategy of aggressive behavior in small mammals. Adult male striped hamsters, a solitary and aggressive animal species, were used in this study, in which intruder hamsters were introduced into the home cage of resident hamsters for 10 min per day, using a resident-intruder model. Energy intake and basal metabolic rate (BMR) were measured in resident hamsters and controls that had no intruders, after twenty-one days of resident-intruder tests. The correlations between BMR and masses of inner organs were examined using Pearson’s correlation analysis. The data showed that the resident hamsters increased BMR by 26.2%, and also significantly elevated gross and digestive energy intake compared to their counterparts without aggressive behavior. Body mass, carcass mass, and masses of liver, lung, kidneys, stomach, small intestine and caecum increased significantly in the Resident group compared to Control group. Significant positive correlations were observed between these organs and BMR. These findings suggest that the adaptive energy budget is employed by striped hamsters to meet the aggressive behavior, within which the energy expenditure caused by defensive aggression is compensated by an increase in energy intake. The intensive conspecific aggression between individuals may be one of the factors influencing higher BMR of this species.