The predominant characterization of flow in sport has emphasized athletes’ reports of reduced conscious attention and effort; however, this is difficult to reconcile with other reports of superior focus and lack of distraction. The aim of this study was to explore this tension by testing novel, theoretically driven predictions for subjective and objective mental effort and by assessing visual attention control using an experimental research design. Specifically, we predicted that perceived and actual effortful attention might dissociate across 3 conditions of a simulated car-racing task designed to manipulate the level of flow: too easy, matched to skill (flow), and too difficult. Task absorption, objective mental effort, and focused gaze were all highest in the matched condition. However, objective performance, reported fluency, and mental effort demonstrated a linear relationship across conditions (participants performed worse and reported more effort and less fluency as difficulty increased). These results suggest a dichotomy between objective and reported effort and suggest that flow is underpinned by efficient attentional control.