Imagery Rescripting (ImRs) is a therapeutic technique that alters the meaning of aversive memories, thereby changing the encapsulated beliefs of the individual. While ImRs has been shown to be effective, its underlying mechanisms remain unclear. This study aimed to investigate a potential mechanism through which ImRs alleviates distress associated with aversive memories. We hypothesized that changes in memory negativity predict changes in memory-related distress, which may be explained/mediated by changes in encapsulated beliefs. Furthermore, we proposed that meta-emotions—beliefs about one’s own emotions—moderate both the relationship between memory negativity and encapsulated beliefs, and the relationship between encapsulated beliefs and memory distress. The study recruited 43 non-clinical student participants and used a within-subject design. Participants completed an online screening, followed by three lab sessions: pre-test, ImRs intervention with post-test, and a follow-up session. Data was collected via structured interviews and self-report measures by supervised clinical psychology master’s students. Moderated mediation analyses indicated that changes in memory negativity significantly predicted changes in memory-distress, but found no evidence for mediation through encapsulated beliefs or moderation by meta-emotions. These results suggest that reductions in memory negativity play a crucial role in alleviating memory distress following ImRs. This highlights the importance of focusing on the negativity of aversive memories to reduce distress, potentially simplifying intervention strategies.