This study examined the effect of supplementation with concentrated bovine colostrum protein powder (intact™) on plasma insulin-like growth factor I (IGF-I) concentrations, endurance running performance and recovery. Thirty physically active males completed 8 weeks of running training whilst consuming 60 g·day −1 of intact™ powder (n=17) or a concentrated whey protein powder placebo (n=13) in a randomised, double-blind, parallel design. Plasma IGF-I concentrations were measured prior to subjects performing two (∼30 min) incremental treadmill running tests to exhaustion (RUN1 and RUN2) separated by 20 min of passive recovery at Weeks 0, 4 and 8. Plasma IGF-I concentrations showed little change in either group (p=0.83). Effective peak running speed (PRS E ; i.e. equivalent of peak power) during RUN1 was not different between groups at Week 0 (p>0.99), and had increased by a similar amount in both groups by Week 4 (mean±SD, intact™ 2.2±4.0%, placebo 3.2±3.3%; 95% confidence interval [95% CI] 15.7 to −13.7%; p=0.89) and Week 8 (intact™ 3.6±5.6%, placebo 3.4±4.4 %; 95% CI −100.0 to 100.0 %; p>0.99). PRS E was less in both groups during RUN2 (p<0.05), but was not significantly different between groups at Week 0 (p>0.99). PRS E during RUN2 tended to have increased more in the placebo group by Week 4 (intact™ 1.8±4.8%, placebo 4.2±3.9%; 95% CI 0.2 to −5.0%; p=0.07), but the intact™ group had increased PRS E significantly more by Week 8 (intact™ 4.6±6.1%, placebo 2.0±4.5%; 95% CI 0.0 to 5.2%; p=0.05), resulting in a significantly faster PRS E (p=0.003). We conclude that supplementation with intact™ powder did not increase plasma IGF-I concentrations or improve performance during an initial bout of incremental running to exhaustion in our sample. However, performance during a second bout of exercise may be improved by as much as 5.2% in the average subject after 8 weeks of supplementation, possibly due to an enhancement of recovery.