Background: Sleep dysfunction is associated with exposure to potentially traumatic events (PTEs), and posttraumatic stress disorder (PTSD) symptom severity. Social support modifies the effect of adversity on health outcomes. Research examining this association within migrant communities is scarce. The present study aimed to assess the psychometric validations of the Filipino version of Pittsburgh Sleep Quality Index (PSQI) and explore whether social support modifies the effect of the relationship between PTSD and sleep dysfunction among Filipino domestic workers (FDWs) in Macao, China. Methods and results: In study 1, exploratory factor analysis and confirmatory factor analysis were conducted for PSQI among 1363 FDWs. The findings validated the two-factor structure (“perceived sleep quality” and “sleep efficiency”) of PSQI to assess the sleep disturbances of subjective sleep reports among FDWs. In study 2, a total of 131 FDWs with snowball sampling completed a baseline assessment, along with 10-day Actiwatch2 assessment with accompanying self-reported electronic daily sleep dairy. A subsample of 61 participants completed a PSQI follow-up assessment after 10 days. The psychometric validity of PSQI was assessed by the internal consistency, 10-day test-retest reliability, convergent validity comparing with baseline depression and anxiety, and 10-day averaged sleep parameters from sleep dairy and Actiwatch2, and discriminant validity comparing with baseline measures of daytime sleepiness, rumination, social support, and self-reported height. The results supported that PSQI factors scores and ‘subjective sleep quality’, ‘sleep latency’, and ‘sleep duration’ component scores are valid measures of sleep dysfunction among FDWs. In study 3, a cross-sectional study of 1363 FDWs were recruited using respondent-driven sampling. PSQI “perceived sleep quality” was significantly associated with the frequency of PTEs exposure and PTSD symptoms. PSQI factor “sleep efficiency” was significantly iii associated with social support from family and friends. Regression analyses demonstrated that after adjustment for covariates, no interaction between PTSD severity by social support from family and friends was significant. Conclusions: The present study suggested that the Filipino version of PSQI with two factors was valid to assess sleep dysfunctions among FDWs. Future studies are needed to better understand the mechanism linking various sources of social network with sleep dysfunction.