<strong>Purpose:</strong> We explored parents’ perceptions and judgment formation processes concerning their infants’ health-related quality of life (HRQOL). <strong>Method:</strong> The PedsQL<sup>TM</sup> Infant Scales—an instrument specifically designed for infants aged 1 - 24 months—were translated into Japanese. Forward and backward translations were performed, evaluating the semantic and conceptual equivalencies. Parents with infants younger than two-years-old were recruited and interviewed using think-aloud and probing techniques. Participants completed the questionnaire while speaking aloud about what came to their mind, what they thought each question meant, and how they reached each answer. <strong>Results:</strong> Seven mothers and three fathers participated. The median age was 33.4 (28 - 43) years. Four had infants younger than six-months-old. All infants were healthy. Parents’ perceptions of their infants’ HRQOL varied across their ages. Some parents with infants younger than six months experienced difficulty discussing “emotional functioning” and “cognitive functioning” because their infants were too young to articulate the actions mentioned in the items. In those cases, the parents responded, “never a problem”. Seventy-five percent of parents recalled their infants’ daily “physical functioning”, while only 58% recalled “physical symptoms”. Some parents’ perceptions and judgment formation were compromised by their own perceptions. For example, they answered “often a problem” when the items were problematic to themselves instead of to their child. However, many distinguished their infants’ HRQOL from their own perceptions, indicating they understood the intention of the questionnaire. <strong>Conclusion:</strong> Parents’ formed judgement may compromise by their own perceptions. The result of this study will be helpful in improving healthcare communication and interpreting parents’ judgments of their infants’ HRQOL in future studies.