Prebiotic fibre represents a promising and efficacious treatment to manage pre-diabetes, acting via complementary pathways involving the gut microbiome and viscosity-related properties. In this study, we evaluated the effect of using a diverse prebiotic fibre supplement on glycaemic, lipid, and inflammatory biomarkers in patients with pre-diabetes. Sixty-six patients diagnosed with pre-diabetes (yet not receiving glucose-lowering medications) were randomised into treatment (n = 33) and placebo (n = 33) interventions. Participants in the treatment arm consumed 20g per day of a diverse prebiotic fibre supplement and participants in the placebo arm consumed 2g per day of cellulose for 24 weeks. A total of 51 and 48 participants completed the week 16 and week 24 visits, respectively. The intervention was well-tolerated, with a high average adherence rate across groups. Our results extend upon previous work, showing a significant change in glycated haemoglobin (HbA1c) in the treatment group, but only in participants with lower baseline HbA1c levels (<6% HbA1c) (P = 0.05; treatment -0.17 ± 0.27 vs. placebo 0.07 ± 0.29, mean ± SD). Within the whole cohort, we showed significant improvements in insulin sensitivity (P = 0.03; treatment 1.62 ± 5.79 v. placebo -0.77 ± 2.11), and C-reactive protein (PFWE = 0.03; treatment -2.02 ± 6.42 vs placebo 0.94 ± 2.28) in the treatment group compared with the placebo. Together, our results support the use of a diverse prebiotic fibre supplement for physiologically relevant biomarkers in pre-diabetes.