Background: In most developing countries, the body temperature of children is routinely measured through the axilla because it is convenient. However, concerns have been raised concerning the reliability of axillary temperature in screening for fever especially in under five children. Objective: This study was carried out to determine the reliability of axillary temperature in screening for fever in under five children. Materials and Methods: This cross-sectional study was carried out at the Paediatric Department of Federal Medical Centre, Owerri, Imo State. Eligible children were consecutively recruited. Rectal and axillary temperatures were taken simultaneously in each eligible child with a mercury-in-glass thermometer. Statistical analysis was done using SPSS version 20. Results: A total of 156 children were recruited and the children were aged 1 day to 59 months. There were 81 males and 75 females. There was a positive correlation between rectal and axillary temperature. Using the rectal temperature as gold standard, the sensitivity and specificity of axillary temperature was 88.6% and 89.6% respectively. Conclusion: The high sensitivity and strong positive correlation between axillary and rectal temperatures show that the axillary temperature can reliably screen for fever.