Background: Acculturation is a dynamic stress process for those undergoing migration. To date, the association between acculturation and the processing of traumatic events has not been empirically explored despite those concepts being both associated to stress. Objectives: We explore the relationship between acculturation, the cognitive processing of traumatic events and mental health outcomes Methods: The sample consisted of 161 migrants living in the UK. A k-means cluster analysis was used to classify participants based on their level of acculturation. Analyses of covariance (ANCOVAs) and regression analyses were used to analyse cross-sectional data. Results: Three clusters were identified from the data: higher and easier acculturation (HEA); higher and harder acculturation (HHA); and lower acculturation (LA). Gender and trauma exposure were identified as significant covariates. There were significant effects of acculturation on post-traumatic personal and public negative appraisal measures, and on post-traumatic and depression symptoms. Individuals in the LA cluster presented significantly higher scores on these measures compared to the other two clusters. An exploratory mediation analysis revealed that post-traumatic, depression and anxiety symptoms can be predicted by acculturation through the mediating role of post-traumatic negative appraisals, with significant differences between HEA cluster and LA cluster, and between HHA cluster and LA cluster. Conclusions: Overall, these findings shed light on the role of acculturation on the processing of traumatic events and subsequent mental health symptoms, both at the intrapersonal and the interpersonal level. That individuals with lower acculturation display clinical levels of mental health symptoms and more negative appraisals warrants the exploration of acculturative process in therapy.