Introduction: The aim of current study was to compare dietary diversity score (DDS) among obese, overweight and normal-weight Tehranian adults. Materials and Methods: This was a case-control study conducted on 200 cases (100 obese and 100 overweight) and 300 controls, all aged over 18 years with (normal-weight matched by socioeconomic status), in Tehran. The study was based on self-administered questionnaires, including a 168-item semi-quantitative food frequency questionnaire (FFQ), a simple self-report physical activity questionnaire and a sociodemographic questionnaire. DDS was computed based on the scoring of the five food groups of the United States Department of Agriculture (USDA) food guide pyramid according to the Kant et al method. Anthropometric measurements including height, weight, waist and hip circumferences were measured and body mass index (BMI) and waist-to-hip ratio (WHR) were calculated. Results: Mean DDS in obese (5.65±1.32) was higher than in overweight participants (5.23±1.23) and that of overweight participants was higher than normal-weight ones (4.97±1.42), (P<0.001). The odds of obesity increased with increase of each one unit of DDS (OR,1.46; 95%CI,1.22-1.74) and slightly weakened after adjusting for age, sex, marital status, smoking, socioeconomic status, physical activity and energy intake (OR,1.34; 95%CI,1.07-1.68). Conclusion: There was a significant positive association between DDS and obesity among Tehranian adults, emphasizing the need for more  investigations to recommend increasing dietary diversity to improve health in adults.