Background: Under nutrition is important cause of childhood morbidity and mortality. In India burden of underweight children in under 5 years of age is still 35.7% (NFHS-4) and is 22% in Punjab which is still considered to be a major public health problem. Thus this study was planned to find prevalence and risk factors of under nutrition in under 3 children in urban Ludhiana.Methods: It is community based cross-sectional study conducted in under 3 year children in field practice area of Urban Health Centre under Department of Community Medicine, Dayanand Medical College, Ludhiana. Minimum sample size of 368 was calculated. Data was collected from routine surveillance by ANMs in their visits to area. Under nutrition was taken as weight for age as per standard growth chart used in India (WHO based). Statistical analysis: Microsoft Excel, Chi square test, SPSS.Results: Out of 387 children, 82 (21.2%) were underweight [17 (4.4%) severely and 65 (16.8%) moderately underweight]. Increasing age, partial immunization, low birth weight and high birth order were significantly associated, while gender, type of family, SES, mother’s BMI & literacy and exclusive breast feeding were not significantly associated with prevalence of underweight.Conclusions: Increasing age, partial immunization, low birth weight and high birth order were all significantly associated with underweight. Maternal and child health services need to be strengthened.