Malnutrition is widely prevalent among hospitalized children in most developing countries including Bangladesh. Though malnutrition accounts for the high rate of under 5 mortality sometimes it is overlooked. Keeping in this in mind A comparative cross sectional study was done in Mymensingh Medical College Hospital from 1st October 2009 to 31st May 2011. Children aged 1-5 years with presence of one or more criteria WHM <70%, WHZ-score <-3SD, Bipedal edema & Mid upper arm circumference <110mm were taken as study group and children aged 1-5 years with normal growth allowable normal range of variation is between 3rd and 97th centile curve or median (50th centile) ±2SD of weight for age growth chart (CDC growth chart, USA, 2000) were taken as reference group. Persistent diarrhea, Patients taking medications containing zinc, copper, magnesium, phosphorus & calcium, PEM with shock were excluded from study group. Nutritional assessment was done according to WHO criteria of SAM. Serum Zinc, Copper Magnesium and Phosphorus level were determined by Atomic Absorption Spectrometry using UNICAM - AA Spectrometer, model no. 969, Spain. Total 120 study populations were taken. Ninety Out of 120 were taken as a study group (SAM) & 30 were reference group. In reference group serum Zn, Cu, Mg, P value was 103.80±8.86μg/dl, 135.92±13.57μg/dl, 2.31±0.18mg/dl, 3.96±0.22mg/dl respectively. In study group serum Zn, Cu, Mg, P value was 60.33±11.08μg/dl, 80.60±15.46μg/dl, 1.47±0.22mg/dl, 2.00±0.52mg/dl respectively. All these results show that there is significant difference between study group & reference group. Considering the decreased level of these parameters, close biochemical monitoring and follow up should be emphasized for the children with SAM.