Objectives This study was conducted to determine whether nano-sized carbon black exposure results in greater damage in high fat diet-induced overweight rats than normal weight ones and to identify the possible causes of any differences. Methods Two groups of Sprague-Dawley rats allocated by body weight (normal and overweight) were exposed to aerosolized nano-sized carbon black for 6 hours a day, 5 days per week over a 4-week period. Differential cell counts, lactate dehydrogenase (LDH) activities and albumin concentrations were measured in bronchoalveolar lavage (BAL) fluid, and histopathological findings in the lungs were evaluated. Tumor necrosis factor-alpha (TNF-${alpha}$) and interleukin (IL)-6 were measured in BAL fluid and supernatants of lipopolysaccharide(LPS)-stimulated lymphocyte culture. Results Rats exposed to high concentrations of nano-sized carbon black showed significantly increased (p <0.05) polymorphonuclear leukocyte number and LDH activity in the BAL fluid from both overweight and normal rats. Mild histopathological changes were observed in normal rats irrespective of carbon black concentrations. However, severe histological scores were found in overweight rats ($1.75{pm}0.46$, $2.25{pm}0.46$, and $2.88{pm}0.35$ after low, medium, and high concentration exposures). Proinflammatory cytokine levels of TNF-${alpha}$ and IL-6 were significantly higher in the supernatant of LPS-stimulated lymphocytes of overweight rats, whereas there was no significant difference in the BAL fluid between normal and overweight rats. Conclusions Inflammation and damage to lungs exposed to nano-sized carbon black was more severe in high fat diet-induced overweight rats compared to normal rats.