Aim <p>This study used ecological momentary assessment to examine the moderating effect of cultural variables (cultural group and self-construal) on the association between rumination and affective outcomes among European Australian and Chinese Australian trauma survivors.</p> Method <p>European Australian (<i>n</i> = 46) and Chinese Australian (<i>n</i> = 49) trauma survivors were recruited through social media advertisements and completed baseline measures of posttraumatic stress disorder (PTSD) symptomatology and self-construal before completing daily measures of rumination and positive (PA) and negative (NA) affect (4 times per day for 7&#xa0;days; 2239 observations).</p> Results <p>First, rumination (brooding, reflection, trauma-related) was significantly associated with lower levels of momentary PA and higher levels of momentary NA regardless of cultural group. Self-construal moderated these associations for specific forms of rumination. Second, PTSD symptoms moderated the positive relationships between brooding and PA, and between trauma-related brooding and NA, with these associations being stronger at higher levels of PTSD symptomatology. There was no evidence that cultural group moderated the relationship between any type of rumination and affect, regardless of PTSD symptom level. However, self-construal was found to moderate the association between reflection and trauma-related brooding and affect, at various levels of PTSD symptomatology.</p> Conclusions <p>This study highlights that the relationships between PTSD symptoms, rumination and affect may be similar across cultural groups, suggesting that the pathological mechanisms of rumination may supersede the influence of cultural background. However, individual variation in culturally derived values like self-construal may shape relationships under some conditions. Future research is needed to better understand these cultural influences. </p>