Heart rate variability biofeedback (HRVBF) is the training to increase vagally-mediated heart rate variability (vmHRV), accompanied by slow-paced breathing and feedback of heart rhythm. It has been reported to be effective for emotion and cognition. In recent years, increased attention has turned toward participant characteristics as factors affecting HRVBF training effects. Focusing on neural basis commonalities between the mechanisms of HRVBF training effects and processing interoception, this study comprehensively measured interoception and examined the relationship between interoception and cardiac coherence reflecting HRVBF effects. Fifty-four healthy young participants were recruited, and subjective interoception was measured using the Japanese version of Multidimensional Assessment of Interoceptive Awareness (MAIA-J) and the Japanese version of the Body Perception Questionnaire-Body Awareness Very Short Form (BPQ-BAVSF-J), objective interoception using heartbeat counting task (HCT), heart rate variability (HRV), visual exteroception, and the coherence score achieved by HRVBF. We conducted a multiple regression analysis with interoception, HRV, and visual exteroception parameters as explanatory variables and the coherence score as the objective variable. Some subjective interoception and HRV parameters were found to be associated with the coherence score. Our results were consistent with previous studies, showing that higher vmHRV was related to high cardiac coherence. Interoception effects on cardiac coherence may be limited because of the low adjusted coefficient of determination and less selected explanatory variables in the multiple regression analysis. Our results may contribute toward predicting HRVBF training effects and the screening of those who are likely to benefit from the training from the perspective of interoception and vmHRV.