Pediatric delirium has been well investigated and its prevalence is reported to be from 20% to 44%. For pediatric intensive care settings, several validated assessment tools for diagnosing delirium, including the Preschool Confusion Assessment Method for the Intensive Care Unit (psCAM-ICU), are available in English. However, validated assessment tools for identifying pediatric delirium are unavailable in Japanese. Therefore, the aim of this study is to verify the Japanese translation of the psCAM-ICU.We enrolled patients at the Pediatric ICU at University of Tsukuba Hospital (Tsukuba, Japan) from May 2017 to February 2019. Enrollment criteria included patients aged 6 months to 5 years, and we excluded coma patients scoring under -4 on the Richmond Agitation-Sedation Scale or suffering from stroke. Pediatric patient delirium was simultaneously evaluated by three medical workers (pediatric intensivist and researchers). Psychiatrists then verified these findings against criteria of the Diagnostic and Statistical Manual of Mental Disorders - 5th Edition. We evaluated criterion validity (sensitivity and specificity) and reliability using Cohen's κ coefficient.We made a total of 56 independent assessments of 19 patients (42% female) with an average age of 18 (±15) weeks. Mechanical ventilation was used at least once in 73% of patients and the positive rate of delirium was 54% in total observation. Overall, the psCAM-ICU showed high sensitivity, specificity (sensitivity, 0.90 [95% confidence interval [CI], 0.80-0.94]; specificity, 0.93 [95% CI, 0.83-0.97]), and high reliability within the researcher assessments (κ = 0.92; 95% CI, 0.82-1.0).We verified the psCAM-ICU and it shows high validity and reliability.