The present cross-sectional study was conducted to evaluate mid-upper arm circumference (MUAC) based undernutrition among Bengalee preschool children. This study was undertaken among 656 (326 boys; 330 girls) 3-5 years old rural Bengalee preschool children of Sagar Block, South 24 Parganas District, West Bengal, India. The MUAC was recorded according to standard procedure and nutritional status was evaluated using the World Health Organization (1995) guidelines. Age combined sex-specific mean values of MUAC among boys and girls were 14.58 (±0.90) cm and 14.48 (±0.85) cm respectively. Significant sex difference was observed at the age of 4 years (t=3.88, P=<0.001). Significant age variations were also found in mean MUAC. The overall prevalence of undernutrition was 25.61 percent. Boys (28.83%) were more undernourished than girls (22.42%). Prevalence of moderate undernutrition was more prevalent than severe undernutrition. Appropriate effective measures should be undertaken to reduce this undernutrition.