Thiamine deficiency may be associated with severe acute malnutrition (SAM) and contribute to its clinical signs and complications. This hospital-based prospective study aimed to determine if thiamine deficiency is present in children with SAM in Port Moresby General Hospital (PMGH). Convenient sampling was used to select 208 children aged between 2 months and 13 years (median age 15 and IQR 11-32 months) presenting to the Children’s Emergency Department requiring venipuncture for routine testing who had additional blood taken for assay of thiamine levels. Nutritional status was determined using the WHO weight for height (WFH) z-scores. Details of socioeconomic background and diet were recorded. Thiamine levels were determined using enzyme-linked immunosorbent assay (ELISA) test kits. A total of 158 (76%) of the 208 samples were satisfactory for analysis; 86 (54%) from children with normal WFH, 26 (17%) from those with moderate malnutrition and 46 (29%) from those with severe malnutrition. Thiamine levels were normally distributed overall. The mean was 34.18  5.8 ng/ml. This was within the reference level of 16-48ng/ml. There was no statistically significant difference in levels between the normal, moderately and severely malnourished children (33.6  5.6, 35.3  5.7 and 34.4  5.7 ng/ml). The assay of thiamine levels in serum using ELISA is not the best method for determining thiamine deficiency and further studies using whole blood and high-performance liquid chromatography are needed