Background: Undernutrition is a major health and nutrition problem in India especially among preschool children. It is an important cause of childhood mortality and morbidity and also leads to permanent impairment of physical and mental growth of those who survive. The objective of the study was to estimate the prevalence of undernutrition among preschool children in the study setting and to determine various factors associated with undernutrition of the child.Methods: A cross sectional study was conducted among 400 preschool children in the field practice area of PHC Aaynoor, Shivamogga, Karnataka. Cluster sampling technique was used for sample selection. Data was collected by interviewing the parent /guardian using a pretested and semistructured questionnaire and anthropometric measurements were done as per standard techniques. Statistical analysis was done using WHO Epi-info software version 3.5.4.Results: The prevalence of underweight, stunting and wasting was observed in 38%, 43% and 15.8% of children respectively. The study found significant association between the prevalence of undernutrition and gender, birth weight, birth order, number of siblings, caste, paternal literacy and availability of toilet in the house of the child.Conclusions: The present study revealed that the problem of undernutrition is critical in the study area and identifies multiple risk factors for its causation, thereby signifying a well - coordinated multi sectorial approach to curb the same.