Intolerance of Uncertainty (IU) is a dispositional tendency to react negatively to uncertainty. The Intolerance of Uncertainty Scale for Children (IUS-C) is designed to measure IU in children but there has been limited investigation into the psychometric properties of this scale. Using data from 227 preadolescent children and 204 parents, we examined (a) readability and whether any items were difficult to understand for children and parents, (b) factor structure, (c) test-retest reliability, and (d) the agreement between child and parent forms of the IUS-C. Results revealed that the reading age of the IUS-C may be too high for preadolescent children and that both children and parents found some items difficult to understand. Model fit with the full IUS-C was not adequate for either parent or child forms. For both forms, selecting items aligned with the IUS-12 led to adequate model fit. For both child-report and parent-report, a one-factor model was supported. Test-retest reliability of total score for all versions was high over a 2-week period (child form: ICC = .82 for 27 item and ICC = .73 for 12 items; parent form: ICC = .87 for 27 item and ICC = .86 for 12 item) but agreement between child and parent forms was consistently poor (r = .24 for 27 item and r = .29 for 12 item). Overall, the results suggest that IUS-C-12 is most appropriate for preadolescent children and their parents. The reading age remains slightly high for preadolescent children so it may be beneficial for future research to consider developing a child-report version with lower reading age.