Background: Patients with single ventricle heart disease are living into adulthood due to medical and surgical advancements but have significant physical comorbidities and an increased risk for psychological comorbidities compared to healthy subjects or those with other CHD diagnoses. This study aimed to systematically review psychological functioning in paediatric single ventricle heart disease. Methods: Literature was searched using PubMed, Embase, PsycInfo, CINAHL Complete and Scopus. Peer-reviewed articles that included patients ages 0–25 years with single ventricle heart disease, and quantitative measures of psychological outcomes were included. Meta-analysis using a fixed-effect model was conducted for internalising and externalising t-scores, utilised by the Achenbach Child Behavior Checklist. Results: Twenty-nine records met the criteria for inclusion. 13/24 studies demonstrated increased risk for internalising disorders, such as anxiety/depression; 16/22 studies demonstrated risk for externalising disorders, such as attention or behavioural problems. Meta-analysis of four studies revealed that paediatric single ventricle heart disease patients had no significant difference in internalising and externalising t-scores compared to normative values. Conclusions: The current review demonstrates the need for further studies to better understand psychological functioning in patients with single ventricle heart disease, with a majority of studies showing increased risk for psychological problems despite no difference seen in a small meta-analysis. This summary of the literature underscores the need for regular psychological screening, earlier intervention and integrated mental health therapies in paediatric single ventricle heart disease.