The exact role of boron in humans is not known although its supplementation causes several important metabolic and inflammatory changes. The objective of this study is to evaluate the possibility of an association between blood boron level and obesity in normal, overweight, obese, and morbidly obese subjects. A total number of 80 subjects, categorized into four groups based on their body mass index as normal, overweight, obese, and morbidly obese, were enrolled in this study. Age, sex, body mass index, and blood boron levels were recorded for each subject. Although the distribution of female and male subjects and blood boron levels were similar between groups, the mean age of normal subjects was significantly lower than the others (p = 0.002). There was a significant relationship between age and quantitative values of body mass index for each subject (beta = 0.24; p = 0.003). In addition, between blood boron levels and quantitative values of body mass index for each subject, a significant reverse relationship was detected (beta = -0.16; p = 0.043). Although age seemed to be an important variable for blood boron level and body mass index, blood boron levels were shown to be lower in obese subjects in comparison to non-obese subjects.