Background: Protein Energy Malnutrition (PEM) is widely prevalent form of malnutrition among under five children and is still the major problem in our country especially in urban slums. Objectives: 1) To estimate the prevalence of PEM in children aged 1 to 5 years. 2) To study the association of immunization status and common morbidities on PEM of children aged 1 to 5 years Methods: A cross sectional study of 600 children of 1-5 year age group in urban slums of Mysore city was carried out with cluster random sampling method. The data was collected using a predesigned and pretested proforma. Clinical examination and anthropometry was used to assess nutritional status. WHO child growth standards, 2006 reference data were used to classify malnutrition. Results: Among 600 children examined, 285 (47.5%) were males and 315 (52.5%) were females. 560 (93.3%) had received primary immunization, while 40 (6.7%) children were partially immunized.Diarrhoea and ARI werereported in 222 (36.9%) and 83(13.8%) of children respectively during the past one month. The prevalence of underweight, stunting and wasting was 129 (21.5%), 135 (22.5%) and 9 (7.5%) respectivelyPrevalence of PEM was found to be higher in children who were partially immunized and was statistically significant. Among the children with history of ARI 64 (77.1%) were found to be underweight, 57 (38.7%) were stunted and 24 (58.9%) were wasted and was statistically significantly (p < 0.05). Underweight, stunting and wasting were seen in 119 (53.6%), 120 (54.1%) and 38 (17.1%) children respectively among children with history of diarrhoea and it was statistically significant. Conclusion: Immunization status and common avoidable morbidities like Acute respiratory tract infection and diarrhea plays an important role in nutritional status of the child.