Athletes often undertake intensified training loads prior to competition with the goal of functionally overreaching for temporary performance enhancement; however, little is known about the impact of this on cognitive function. The aim of this study was to investigate the effect of intensified training induced fatigue on cognitive function, psychological state and performance in trained cyclists. Twenty-three trained male cyclists were randomly assigned to an intensified training group or a control group for two-weeks, followed by a two-week taper period. At baseline, one-week, two-weeks and post-taper, participants undertook a series of cognitive, performance, mood and recovery-stress assessments. The training intervention significantly increased training volume, load and strain by 108%, 116% and 151% respectively. Peak and mean power output on a maximal test and time trial significantly decreased by 4.8% and 9.4% following the two-week training intervention compared to baseline, in addition to a 169% change in total mood disturbance and significant disruption to recovery-stress balance. No change in any cognitive measure was observed across the study period. Following a two-week taper, performance, mood and well-being measures returned to baseline. Two weeks of intensified training resulted in overreaching as identified by performance and psychological measures. Cognitive function was not sensitive to intensified training promoting caution with its use as a measure for the early identification of overreaching. Highlights: Two-weeks of intensified training significantly increased training volume, load and strain eliciting a state of overreaching in trained male cyclists. Intensified training caused deteriorations in physical performance but did not influence cognitive measures. Mood and recovery-stress balance were negatively affected by intensified training but recovered back to baseline following a two-week taper at a reduced training volume. A two-week taper period following two-weeks of intensified training did not result in improved physiological measures, physical performance parameters or mood above initial baseline values highlighting the need for careful consideration over the purpose, desired outcomes and necessity of intensified training on an individualised basis.