The purpose of this study was to compare the motor proficiency and the physical activity (PA) of preschool children with different body mass index (BMI). Fifty-three preschoolers (26 boys and 27 girls), aged 4-5 years, were divided, according to their BMI, to those with: a) normal BMI, b) overweight children and c) obese children. Their motor proficiency was determined by the ‘Motorik’ Module test battery and their PA was evaluated by using the interview ‘Interviewleitfaden zur Aktivität für Kinder von 4 bis 6 Jahren’. According to the IOTF standards, the 22.6% and 9.4% of the children were categorized, as overweight and obese, accordingly and they had no statistically significant difference in their motor performance, when compared with children with normal BMI. However, the weekly participation in at least 60 min daily accumulation of physical activity, was significant lower (MD=1.80, p<.05) in obese children than normal weight peers. The results of the present study are particularly useful, for those who are involved in pre-school education, as they suggest that physical inactivity is strongly related to obesity in preschool children and notify the necessity of Physical Education in the Greek nursery school.