Problem statement: Cystic fibrosis (CF) is a multi-system, life-shortening autosomal recessive disease that affects more than 70,000 people worldwide. Common co-morbidities of CF include obstructive lung disease, pancreatic insufficiency and diabetes mellitus, which contribute to exacerbated free radical production. Additionally, antioxidant status in CF may be compromised due to CF transmembrane conductance regulator deficiency and malabsorption of fat-soluble micronutrients. Consequently, oxidative stress may play an important role in the pathophysiology of CF. This review, therefore, aimed to quantify CF-related circulatory redox imbalances and summarise their relationships with clinical outcomes. Methods: A protocol was registered on PROSPERO (Reference: CRD42018094241). To quantify the extent of CF-redox abnormalities, systematic searches of the Medline, CINAHL, CENTRAL and PsycINFO databases were conducted. Mean biomarker content in whole blood, plasma, serum or erythrocytes from people with clinically-stable CF and non-CF controls within the included studies were used to calculate the standardized mean difference (SMD) and 95% confidence intervals (95% CI) for meta-analysis. Results: Forty-nine eligible studies were identified, including a total of 1,702 people with CF and 1,583 controls, in which 25 biomarkers were eligible for meta-analysis. Notably, meta-analyses revealed that protein carbonyls (SMD: 1.13, 95% CI: 0.48-1.77), total F2-isoprostane 8-iso-prostaglandin F2α (SMD: 0.64, 95% CI: 0.23-1.05) and malondialdehyde (SMD: 1.34, 95% CI: 0.30-2.39) were significantly higher, and vitamins A (SMD: -0.66, 95% CI -1.14–0.17) and E (SMD: -0.77, 95% CI: -1.31–0.23), β-carotene (SMD: -1.80, 95% CI: -2.92–0.67), lutein (SMD: -1.52, 95% CI: -1.83–1.20) and albumin (SMD: -0.98, 95% CI: -1.68–0.27) were significantly lowered in the plasma or serum of people with clinically-stable CF versus controls. Fat-soluble vitamin concentrations were positively correlated with indices of lung function and nutritional status, and negatively correlated with age and leukocyte counts. Additionally, markers of lipid peroxidation were positively correlated with age and leukocyte count, and negatively correlated with nutritional status. Conclusions: This systematic review and meta-analysis supports the concept that some circulating biomarkers of oxidative damage and antioxidant capacity are abnormal in people with clinically stable-CF versus controls. These observations implicate redox imbalances in the pathophysiology of CF-related lung disease; however, further research is required to fully understand the implications of oxidative stress on clinical practise, and on common co-morbidities such as lung disease, pancreatic insufficiency and diabetes mellitus.