Background: Imagery rescripting (ImRs) is an intervention designed to process emotional memories by imagining outcomes that fulfill unmet needs. ImRs effectively reduces psychopathology and memory distress, although working mechanisms are unclear. Theories suggest that ImRs changes the meaning of the original memory and/or increases an alternative positive or neutral interpretation. Method: In a non-clinical sample, we provided one ImRs session targeting a negative autobiographical memory. We investigated whether need fulfillment during ImRs relates to memory distress changes via changes in the beliefs encapsulated in the memory and/or via changes in alternative beliefs. We also explored whether encapsulated and alternative belief changes pertain to the same process. Results: Frequentist mediation analyses showed that neither belief type is a mediator of the relationship between need fulfillment and memory distress changes. In fact, need fulfillment did not significantly predict memory distress changes. Bayesian mediation analyses provided moderate to strong evidence against a mediating effect for either belief type. Without mediation, we could not evaluate whether encapsulated and alternative belief changes pertain to the same process. Exploratory analyses showed decreases in encapsulated beliefs and memory distress, and increases in alternative beliefs. Discussion: We nuance our conclusions based on previous research, theory, and our study's limitations.