Resumo. BACKGROUND: Several methods are used to induce mental fatigue; predominantly the modified Stroop task, which arguably has little relation to daily lifestyle tasks. AIM: To investigate the influence of the modified Stroop task on mental fatigue, boredom and motor response times. METHOD: 15 subjects (24.3±2.3 years) completed a 30-min modified Stroop task (control condition: 30-min reading) and completed PRE, POST and POST 5-min subjective ratings of mental fatigue, mental effort and boredom. Participants' ability to use congruent and inhibit incongruent precues in a choice reaction time task (CRTT) was measured pre- and post- Stroop and control. RESULTS: Significantly higher subjective ratings of pre-post condition mental fatigue (pre:2.43±1.31 AU, post: 6.42±2.08 AU,p<0.01) and boredom (PRE: 1.65±1.49 AU, POST: 5.03±2.92 AU,p<0.01) were reported following the modified Stroop task condition compared to the control condition mental fatigue (PRE: 1.62±1.17 AU, POST: 2.10±0.92 AU,p>0.05) and boredom (PRE: 1.94±1.52 AU, POST: 3.32 ± 1.66 AU,p>0.05). No significant differences were found between conditions for the extent to which participants’ response times were affected by congruent (p=0.481) or incongruent (p=0.225) precues. CONCLUSION: Future research must adopt cognitive activities with higher contextual interference for greater ecological validity, and elucidate the impact of rest on recovery from mental fatigue.