Obesity status differs by socio-demographic factors, but data for Cyprus are scarce. An in-depth understanding of this relationship may be useful in designing public health programmes. The objective of the present study is to estimate overweight and obesity (OW/OB) prevalence among children and adults in Cyprus and identify related socio-demographic variables. National cross-sectional study of 1140 children (mean age 11 ± 0.98 years) and their parents (mean age 42.5 ± 5.8 years, total n = 1954). Obesity was defined according to the World Health Organization classification for adults and according to IOTF (International Obesity Task Force) criteria for children. Overweight and obesity prevalence among girls was 18.3% and 2.9%, respectively, while in boys, 19.0% and 6.0%. Among parents, OW/OB prevalence was, respectively, women, 22.6% and 5.8%; men, 47.1% and 14.1%. Logistic regression analysis in both children and adults revealed that the most important socio-demographic predictors of obesity status are factors of built environment. Higher prevalence of OW/OB was observed in adults living in a house as opposed to an apartment, in older adults, in younger children, and in men, irrespective of age. There is a severe obesity problem in the Cypriot population; almost one in two adults and at least one in four preadolescent children are overweight or obese. Prevalence of OW/OB was related to socio-demographic factors, especially among adults and women.