This study tested psychometric properties of the Children's Moods, Fears and Worries Questionnaire (CMFWQ) with a population sample of children at risk for developing internalizing problems. The CMFWQ was completed by 489 parents of 5‐year‐old children who had been screened for temperamental inhibition in preschools across eight government areas of Melbourne, Australia. Parents also completed the Strengths and Difficulties Questionnaire (SDQ) and Anxiety Diagnostic Interview Schedule (ADIS‐P‐IV). In this inhibited sample of children, the CMFWQ showed high internal consistency of items (α = .95). The CMFWQ demonstrated convergent validity with the SDQ ‘emotional symptoms’ subscale and discriminant validity with the ‘conduct problems’ subscale. Supporting criterion validity, the CMFWQ significantly distinguished between groups of inhibited children with versus without ADIS anxiety disorders. Psychometric properties of the CMFWQ now extend to young inhibited children who are at risk for developing internalizing problems as they grow. Copyright © 2016 John Wiley & Sons, Ltd.