Delays in child growth or development are significant problems for children, their families and population health. Eliciting parental concerns as early as possible to promote child growth and development requires close collaborative working with parents. There is evidence that parents delay expressing concern and that health-care professionals are not always effective at eliciting and attending to parental concerns. The aim of this study was to understand the experiences of parents of preschool children who had expressed a child growth or development concern. An Interpretative Phenomenological Analysis (IPA) study design was used with a purposive sample of parents of 15 preschool children in Ireland. Data were collected by semi-structured interviews and analysed using IPA. One key superordinate theme – Uncertainty – ‘a little bit not sure’ captured how parents made sense of their concerns about their child’s growth and development. In addition to watching, comparing and wondering, parents assessed whether their child could ‘do other things’ or if something in particular could have caused the growth or development problem. Parents, particularly mothers, grapple with uncertainty associated with unfamiliar cues in the complex and multifaceted nature of child growth and development in their efforts to make sense of what is happening with their child.