Growing work suggests that interoception, i.e., representations of one’s internal bodily changes, plays a role in shaping emotional experiences. Past studies primarily examine how behavioral accuracy in detecting interoceptive signals (interoceptive ability) relates to emotion, with less work examining self-reported interoceptive facets such as the self-characterizations of one’s interoceptive abilities (interoceptive sensibility) or evaluative beliefs about the value vs. danger of interoceptive signals (interoceptive beliefs). However, existing studies tend to be small and rarely examine physiological reactivity, behavioral, and self-reported dimensions of interoception together in the same sample. As such, it remains unclear whether and how much individual differences in interoceptive facets uniquely and in interaction with physiological reactivity may matter in relation to emotional experience. Herein, 250 healthy young adults completed a laboratory visit with the Whitehead heartbeat detection task (assessing interoceptive ability) and questionnaire measures of interoceptive sensibility and beliefs. At a follow-up session, 227 participants returned to undergo an acute psychosocial stressor with physiological reactivity measures (pre-ejection period, heart rate variability). Immediately after the stressor, individuals self-reported their emotions. Linear regressions revealed that greater sympathetic nervous system reactivity (i.e., pre-ejection period), poorer interoceptive ability (i.e., accuracy), and less positive interoceptive beliefs were related to more intense (particularly, high arousal) emotions during the stressor. Importantly, across models, interoceptive beliefs showed the largest, most consistent main effects and interactions with physiological reactivity (pre-ejection period, heart rate variability). Implications for psychological theories of and individual differences in emotion, stress, and interoception are discussed.