Aim To examine the within-person variability in plasma glucose responses to moderate-intensity morning exercise in young individuals with type 1 diabetes after overnight fasting and under basal insulin conditions. Methods In this pilot study, eight participants completed 40 min of moderate-intensity exercise at 60% V?O-2 peak on three separate days. The within-person standard deviation (SDw) in plasma glucose response was analysed both during and 1 h after exercise using the two visits per participant most closely matched by pre-exercise plasma glucose level. Results When the two closest matched visits per individual were included for analysis, mean (+/- SD) change in plasma glucose level was -1.8 +/- 1.1 mmoL/L during exercise and -0.6 +/- 1.0 mmoL/L during recovery, with the SDw of these changes being 0.5 mmol (95% CI 0.2, 0.8) during exercise and 0.8 mmoL/L (95% CI 0.4, 1.3) during recovery. The median intra-individual difference in plasma glucose level change was 0.3 mmoL/L [IQR 0.1, 0.7] during exercise and 0.8 mmoL/L [IQR 0.4, 1.0] during recovery. Conclusion Within-person plasma glucose responses to moderate-intensity exercise may be reproducible under fasting and basal insulin conditions and similar pre-exercise plasma glucose levels. This finding may assist the design of future studies investigating both the reproducibility of glycaemic responses to exercise and blood glucose management for individuals with type 1 diabetes.