AIMS: Interoception is the sensing function of physiological conditions and is crucial in self-regulation and decision-making. We examined the association of heartbeat tracking task performance, an indicator of interoceptive accuracy, with the degree of improvement in exercise tolerance in patients undergoing home-based cardiac rehabilitation. METHODS AND RESULTS: Participants underwent baseline peak oxygen uptake (VO2) measurements and a heartbeat tracking task. The heartbeat tracking task score varies between 0 and 1, with higher scores indicating a better heartbeat perception. After 6 months of home-based exercise training, peak VO2 was measured again, and the percentage change (%Δ peak VO2) relative to the peak VO2 at baseline was calculated. Univariate regression analysis was performed to examine the association between %Δ peak VO2 and the heartbeat tracking task score. Multiple regression analysis was performed to determine the predictors of %Δ peak VO2. Of 120 participants, 100 patients (age 65.9 ± 11.9 years; 86% male) were included. There was a significant positive association between %Δ peak VO2 and the heartbeat tracking task score at baseline (R 2 = 0.236, P < 0.001). In multiple regression analysis, the percentage of measured peak VO2 to the predicted value (%predicted peak VO2) (β = -0.248, P = 0.002), exercise adherence (β = 0.364, P < 0.001), and heartbeat tracking task score at baseline (β = 0.372, P < 0.001) were significantly associated with %Δ peak VO2. CONCLUSIONS: Heartbeat tracking task performance, an indicator of interoceptive accuracy, at baseline is associated with the degree of improvement in exercise tolerance.