While theoretical models have established the bidirectional relationship between health and wellbeing of parents and children with chronic health conditions (CHCs), previous work has predominantly emphasised the impact of parent functioning on child outcomes. This study examines how quality of life (QoL) domains in children with CHCs are associated with unmet supportive care needs (SCN) of their parents and explores whether these associations vary by health condition. Parents of children with congenital heart disease (CHD), type 1 diabetes (T1D) and cancer diagnosed before the age of 12 years and receiving treatment within the last 5 years were eligible. Parents recruited through charity organisations and social media platforms completed a secure, online survey via Qualtrics. The PedsQL examined child QoL across four dimensions: physical, emotional, social and school functioning. A 34-item survey assessed parents' unmet SCN in the previous month across six need domains (e.g., care and informational). Linear regressions examined associations between child QoL and unmet SCN domains and moderation analyses determined whether associations varied as a function of CHC. The study included 186 parents (age range 25-56 years) of children diagnosed with various CHCs (52% CHD; 27% T1D, 21% cancer). The child's emotional functioning was inversely related to all unmet SCN domains, social functioning was inversely related to three domains (physical and social; support; financial), school functioning was inversely related to two domains (physical and social; care), and child's physical functioning was not associated with any SCN domains. Only the association between child school functioning and unmet care needs was significantly moderated by CHC type (p < 0.05). Poorer emotional functioning in children with a CHC is a key factor in determining parents unmet SCN. Larger studies are required to replicate these findings and inform design of interventions addressing QoL and unmet SCN in families of children with common CHCs.