Background: Trends in obesity have been reported to level off in several Western countries. The aim of this study was to investigate trends in body mass index (BMI) and prevalence of obesity between 2002 and 2010 in Stockholm County, Sweden. Methods: Three cross-sectional questionnaires from the Stockholm Health Surveys were used for this study. A total of 31 182, 34 707 and 30 767 men and women aged between 18 and 64 years completed the questionnaire regarding sociodemographic factors, health parameters, physical activity, smoking habits and anthropometry in 2002, 2006 and 2010, respectively (response rate: 62.5, 61.3 and 55.6%, respectively). Linear regression was used to investigate changes in mean BMI. Relative risk regression models were used to investigate changes in prevalence of obesity, defined as BMI ≥ 30 kg/m2. All analyses were stratified on age and further adjusted for smoking, education and socioeconomic position. Results: Between 2002 and 2006, a stabilization was found in BMI and prevalence of obesity in both men and women. But from 2006 to 2010, BMI and prevalence of obesity had increased, also among the young. In 2010, the prevalence of obesity was 12.2% among men and 10.3% among women. Conclusion: After a period of stabilization in 2002–06, BMI and prevalence of obesity are increasing in Stockholm County, Sweden.