Regulation of cerebral blood flow during exercise in youth is poorly understood. This study investigated the cerebrovascular and ventilatory responses to a ramp incremental cycle test to exhaustion in 14 children (mean ± SD age: 9.4±0.9 y), 14 adolescents (12.4±0.4 y) and 19 adults (23.4±2.5 y). Middle cerebral artery blood velocity (MCAv), partial pressure of end-tidal CO2 (PETCO2) and ventilatory parameters were analysed at baseline, gas exchange threshold (GET), respiratory compensation point (RCP) and exhaustion. Ventilatory efficiency was calculated as the increase in minute ventilation relative to CO2 production during exercise (VE/VCO2 slope). Relative change from baseline (Δ%) in MCAv was lower in children, compared to adolescents and adults at GET (15±10% vs 26±14% and 24±10%, respectively, P≤0.03, effect size (d)=0.9) and RCP (13±11% vs 24±16% and 27±15%, respectively, P≤0.05, d≥0.8). Δ%MCAv was similar in adults and adolescents at all intensities, and similar in all groups at exhaustion. The magnitude of the VE/VCO2 slope was negatively associated with Δ%MCAv at GET, RCP and exhaustion across all participants (P≤0.01, r=-0.37 to -0.58). Δ%PETCO2 was smaller in children and adolescents compared to adults at GET and RCP (P≤0.05, d≥0.6). In children, Δ%PETCO2 and Δ%MCAv were not associated from baseline-GET (r̄=0.14) and were moderately associated from RCP-exhaustion (r̄=0.49). These relationships strengthened with increasing age, and were stronger in adolescents (baseline-GET: r̄=0.47, RCP-exhaustion: r̄=0.62) and adults (baseline-GET: r̄=0.66, RCP-exhaustion: r̄=0.78). This is the first study to compare cerebral blood flow responses during incremental exercise in children, adolescents and adults. Similar increases in cerebral blood flow were observed in adolescents and adults, with smaller increases in children. This study also provides the first evidence on the development of the regulatory role of end-tidal CO2 on cerebral blood flow during exercise during the transition from childhood to adulthood.