Objective: To determine the prevalence of overweight and obesity among children aged 3-5 years at kindergarten and to ascertain the associated factors. Method: This cross-sectional survey included 3343 children aged 3-5 years at kindergarten throughout Nha Trang city. The data were collected from October to November 2010. Result: The overall prevalence of overweight and obesity was 8.4 percent, most of the cases were at grade 1 (59 percent). There was no difference between boys and girls. Overweight and obesity rates increase among groups of age (2.0, 8.6 and 11.5 percent for 3, 4 and 5 years old, respectively). Children living in urban area had higher rate of overweight and obesity than those in suburb (10.2 versus 6.2 percent). Weight at birth, nutritive regimen, sedentary lifestyles, parent's career and knowledge seem to be associated factors. Conclusion: The prevalence of overweight and obesity in children aged 3-5 years at kindergarten in Nha Trang city is considered high in comparison to other regions in the country. An education program providing knowledge and babycare skills for the parents is needed to ameliorate the situation.