Cognitive fatigue, a transient cognitive decline, stemming from extended mental and physical activities is well established in conventional contexts. However, its manifestation and self-awareness during digital pursuits as an integrated style of mental/physical activity, notably electric sports (esports), remain underexplored. Here we show that, using virtual football as a representative model for esports, prolonged esports cause cognitive fatigue with pupil constriction, independent of subjective fatigue across players’ expertise. The casual and hardcore esports players engaged in an intensive 3 hours of gaming session. Subjective fatigue reports remained unchanged for up to 2 hours but increased at the 3 hours conclusion, inversely linked to their enjoyment reports, in both players. Executive function assessed by flanker interference decreased after 2 and 3 hours in casual players. The accuracy of flanker task decreased after 2 and 3 hours in hardcore players, despite an initial accuracy edge. Pupil diameter decreased after 2 and 3 hours and correlated with cognitive performance decline, but diverged from subjective fatigue reports in both players. Our findings clearly suggest a disparity between actual cognitive decline and subjective fatigue awareness with esports, transcending levels of player expertise. Pupil constriction is a potential neurobiological marker that integrates divergent cognitive and subjective fatigue during digital engagement.