Interoceptive sensibility, which denotes the self-perceived sensitivity to inner-body sensations, has been associated with the emotional experiences and inferences of others' emotional states. Focusing on the role of interoceptive sensibility in the emotional states and psychological well-being of mothers during caregiving, this study explores how physiological arousal and interoceptive sensibility mediate the association between mother-infant interaction and maternal well-being using an experience sampling method. Infant-directed-singing (IDS) with social touch was used to facilitate mother-infant interaction. Pairs of 2-8-month-old infants and their mothers participated. Mothers in an IDS group (N = 25) and a no-IDS group (N = 26) recorded their and the infant's daily feelings and physiological states using a smartphone application for one month. All participants, including the control group (N = 78) who neither performed IDS nor used the application, answered the Multidimensional Assessment of Interoceptive Awareness questionnaire before and after the recording period. Results indicated that IDS improved mother-infant interactions and positive feelings, enhancing maternal physiological arousal. Increased interoceptive sensibility enhanced infants' positive feelings in the IDS group, whereas in the no-IDS group, it weakened mother's positive feelings, suggesting that maternal interoceptive sensibility mediated the effects of IDS on mother and infant well-being.