Objectives: The EQ-TIPS was developed to measure the Health-Related Quality of Life in infants/toddlers. Considering the rapid development in this period, this study aimed to investigate age-related variations in EQ-TIPS performance. Methods: Data from 551 infants/toddlers living with a health condition were analysed. Infants/toddlers were grouped by age: 0–6 months (n = 100), 6–12 months (n = 95), 12–24 months (n = 147), and 36–48 months (n = 97). Differences in item responses and item correlations across age groups were calculated by Kruskal–Wallis and Spearman’s correlations, respectively. Results: The report of problems was significantly higher for movement, play, and communication in the 36–48-month group compared to the 0–6-month group. There were strong correlations (r > 0.50) across all age groups between play and movement and communication and social interaction/play; neither pain nor eating showed a clear pattern of association. Conclusion: There is an age-related difference in the reporting of items linked to developmental milestones (movement, play, and communication) with most problems reported in the 36–48-month group when deviation from peers and continued dependence on caregivers is notable. Consideration should be given to including broader examples of play in the EQ-TIPS. Redefining the items to represent social communication and/or (social) emotion, rather than communication and social interaction, may be warranted. Future research should explore the psychometric performance of items to further inform item inclusion and/or revision.