OBJECTIVE Clinically validate (Fehring's model) the characteristics of the nursing diagnosis acute pain in 65 hospitalized children. METHODS Cross-sectional study. RESULTS This study resulted in 13 major characteristics (expressive behavior, change of mental state, verbal report of pain, observed evidence of pain, narrowed focus, position to avoid pain, guarding behavior, sleep disturbance, protective gestures, changes in heart rate, changes in muscle tone, changes in respiratory rate, and facial mask) and in 5 minor characteristics (changes in blood pressure, coded report, changes in breathing pattern, distraction behavior, and changes in appetite). CONCLUSIONS Characteristics with R > 0.50 and ≤ 1 were valid in the diagnosis acute pain. CONCLUSIONS Clinical validation studies must be reproduced in different populations.