Emotion regulation shapes not only how people experience emotional events, but also how those events are remembered, with lasting consequences for behavior and well-being. Reappraisal - the reinterpretation of negative stimuli as more positive – boosts encoding of negative episodes due to a deeper engagement with the meaning of emotional content, while attenuating negative affect over time. Among young adults, reappraisal recruits a distinct network of limbic and cognitive control regions that enhance memory for emotional episodes, thus guiding adaptive resolution of similar negative scenarios in the future. Aging is marked by a greater motivation to regulate emotion and preserve well-being, relative to younger adulthood. Yet, little research has examined if reappraisal reduces negative emotion and enhances memory for negative scenarios in ways that may be similar to -or distinct from- those behavioral and neural mechanisms observed in younger adults. Thus, this dissertation addresses a theoretical gap in clarifying the neural substrates of encoding during reappraisal that support long-term emotional memory in both young and older adults. Twenty young (18-29 years) and 19 older (60-75 years) adults underwent incidental encoding of negative and neutral images during an event-related fMRI scan. Participants either reappraised negative images to reduce negative affect or viewed negative and neutral images passively. Recognition memory for images was assessed in the scanner after a 10-minute (i.e., immediate recall), and 4-hour delay (i.e., delayed recall). Recognition of images did not significantly vary by age group or regulatory condition. However, older adults demonstrated higher recognition sensitivity to neutral relative to negative images. Young adults demonstrated greater relative recruitment of distributed frontal/prefrontal, temporoparietal, and occipital regions to support reappraisal, whereas older adults comparatively relied on a small subset of parietal and posterior cortical regions supporting attentional control and visual integration. In an age-invariant manner, greater prefrontal recruitment predicted worse subsequent recognition accuracy, suggesting a tradeoff between top-down cognitive control and mnemonic efficiency during passive encoding of emotional information. Taken together, these findings reveal neural signatures of reappraisal among both age groups that may interfere with incidental memory encoding for emotional experience and regulation.