Background: Fever of unknown origin (FUO) continues to be a diagnostic dilemma for pediatricians because it is often difficult to distinguish clinically between benign and potentially life-threatening causes. The term is best reserved for children with persistent fever >38 ˚c for which a cause could not be identified for more than 1 week. Aim of work: to evaluate a four-stage investigative guideline for the detection of the causes of FUO among children.  Methods: 70 children aged between 6weeeks to 15 years with FUO were enrolled for this study. Graded investigations were done ranging from routine to advanced and/or specific investigations were performed after revision of detailed history and thorough examination. Results: outpatient investigations were done in 8.6% of the cases. The duration of FUO in this study ranged from 12 days to 8 weeks. The causes of FUO were 31.4% bacterial infection and 11.4% viral infection including Covid-19 infection in 7.1% of them, herpes simplex, and glandular fever in 3.4% of them.ENT affection was present in 4.3%, and the cardiac cause was found in 4.3% of the cases. Malignancy was encountered in 10% of the cases. In 21.4% of the cases, the cause of FUO was not diagnosed. In 10% of the cases, connective tissue disease was detected, and auto-inflammatory disease was encountered in 7.1% of the cases. Conclusion: not all cases of FUO should be admitted to a hospital, as some of them can be diagnosed and treated on an outpatient basis,