The aim of this study was to determine the effect of cycle intensity on subsequent running performance and combined cycle–run (CR) performance. Seven triathletes undertook a cycling graded exercise test to exhaustion, an isolated 500-kJ cycle time trial (CTT) and an isolated 5-km running time trial. Then they performed a series of CR tests, at various cycle intensities, followed by an all-out, 5-km run. The CR tests were separated into four categories based on the percentage of the CTT at which the cycle was performed (CR 81–85%, CR 86–90%, CR 91–95%, and CR 96–100%). Running performance was slower during CR 96–100% compared to CR 81–85% and CR 86–90% (20:45 ± 1:19 vs. 19:56 ± 0:40 and 19:46 ± 0:49 min; P < 0.05), but not CR 91–95% (20:19 ± 1:08 min; P > 0.05). CR performance was maximised during CR 96–100% when compared to CR 81–85, CR 86–90 and CR 91–95% (56:37 ± 4:04 vs. 62:40 ± 5:30, 59:53 ± 4:41 and 58:29 ± 4:40 min; P < 0.05). The results suggest that combined cycle and run performance is maximised when the cycle is completed at the highest sustainable intensity.