The aim of this study was to estimate the prevalence of, and socio-demographic factors associated with, overweight and obesity in Botswana. A cross-sectional survey was conducted in 2007 using a multistage sampling method to select a representative sample of 4107 men and 4916 women aged 20-49 years. Logistic regression analysis was used to identify the socio-demographic factors associated with overweight and obesity. Mean BMI values for men and women were 21.7 kg/m2 and 24.4 kg/m2, respectively. Both overweight and obesity levels were higher among women than men. Overall, 23% of women were overweight compared with 13% of men. Obese women constituted about 15% compared with only 3% of men. However, 19% of men were underweight compared with 12% of women. The main socio-demographic factors associated with overweight and obesity were being older, living in a city/town, being married and having attained higher levels of education, and these relationships were statistically significant at the 5% level. Although over-nutrition is prevalent among adult female Botswana, underweight remains an important public health problem for males. Programmes and other interventions aimed at concurrently addressing both under-nutrition and overweight need to be developed.