ABSTRACT Emotional episodes involve partially coordinated changes in experience and autonomic activity, and subjective–physiological coherence appears to vary with aging and physiological stress. Physiological accounts of emotional aging propose that age‐related changes in autonomic and interoceptive function reduce the informativeness of bodily signals, weakening the coupling between feelings and bodily responses. We test whether subjective–physiological coherence is lower in older vs. younger normoxic adults, lower in hypoxic vs. normoxic younger adults, and similar in hypoxic younger adults and older normoxic adults; in secondary mechanism‐oriented analyses, we examine whether heart‐rate variability and cardiac interoceptive accuracy are statistically related to group differences in coherence. We will test these questions in three groups ( N = 120): younger adults in normoxia, younger adults under acute hypoxia (FiO 2 ≈ 12%), and older adults in normoxia. Participants will view emotional images and provide trial‐wise ratings of affect and approach motivation while heart rate and skin conductance are recorded. Emotional coherence will be indexed primarily by within‐person correlations between subjective arousal ratings and autonomic reactivity, with approach motivation and valence examined as complementary subjective dimensions.