Purpose: Illness cognitions are an important mediator between disease and psychological adjustment. This study assessed the psychometric properties of the Illness Cognition Questionnaire (ICQ), adjusted for the parents of an ill child. Methods: Participants were recruited from two multicenter studies: sample 1 included 128 parents of a child diagnosed with acute lymphoblastic leukemia (ALL) (response rate 82 %) and sample 2 included 114 parents of a child diagnosed with cancer (response rate 74 %). Parents completed an adapted version of the ICQ (Illness Cognition Questionnaire-Parent version (ICQ-P)), together with the Profile of Mood States (POMS; sample 1) or the Hospital Anxiety and Depression Scale (HADS; sample 2). The factor structure of the ICQ-P was examined by means of principal component analysis. Cronbach’s alpha for each subscale and correlations between the ICQ-P scales and the HADS and POMS were calculated. The illness cognitions of parents with and without psychological distress were compared. Results: Factor analysis confirmed the hypothesized structure of the ICQ-P in our sample (n = 242). The three scales Helplessness, Acceptance, and Perceived Benefits explained 9.8, 31.4, and 17.9 % of the variance, respectively. Cronbach’s alpha showed adequate internal consistency (.80–.88). Concurrent and criterion-related validity were appropriate. Conclusions: The results confirm that the ICQ-P reliably assesses the illness cognitions of the parents of a child with cancer. Psychologically distressed parents showed less acceptance and more helplessness. The availability of a short and valid illness cognition questionnaire will help clinicians gain insight into parental cognitions regarding the illness of their child, information that might be helpful for targeting interventions.