Object manipulation skills are a rital area for client assessment in occupational therapy, but in-hand manipulation skills are not specifically included in any standardized tests of hand function for children. The In-Hand Manipulation Test (IMT) was developed for use by occupational therapists with preschool and young school-age children. Assessment of the IMT’s content validity was an important precursor to further development of the test. Twenty-four certified occupational therapists rated young children’s performance during administration of the IMT before completing a content validity survey about the test. Overall, the IMT’s content validity was supported by the feedback from the raters. A final test length of 50 items with two trials per item was considered acceptable, provided that the test takes no longer than 20 to 30 min to administer. The therapists were positive about the content and structure of the rating scale and the approach used in presenting activities to the children. Some issues related to functional validity of some skills or the proportions of in-hand manipulation skills were raised. Further development of the IMT for clinical and research use seems warranted. Revisions to the test will be made, and another pilot study will be conducted before normative data collection. Training for administering and scoring the test will incorporate the recommendations on the basis of this study’s results.