Background: Acute kidney injury (AKI) is a common and potentially life-threatening condition. AKI is defined by an increase of serum creatinine by ≥0.3 mg/dL in 48 h or an increase by ≥1.5-fold from a known or assumed baseline or by a decrease of urinary output to less than 0.5 mL/kg/1 hour (h) for 6 h. Objectives: To assess the specificity and sensitivity of urinary calprotectin in early detection of intrinsic AKI. Patients and Methods: This was a cross sectional study that was conducted on 100 children in Pediatric Intensive Care Unit in the Department of Pediatrics, Zagazig University Hospitals. Results: In this study, 39% of our cases were diagnosed with AKI. The current study showed that, regarding urinary calprotectin on first and third day of admission, there was statistically significant increase in calprotectin level when comparing first and third day levels; p value less than 0.001. Regarding validity of Urinary (U) calprotectin, the value of sensitivity was (76.9%), specificity= (76.9%), PPV = (81.1%), NPV = (81.1%), and (79.5%) accuracy. Conclusion: The results of our study show that urinary calprotectin has higher sensitivity and specificity than serum creatinine levels for detecting early stages of intrinsic AKI.