Background <p>Financial strain is a well-established risk factor for poor sleep, yet few studies have examined whether this association varies by race-ethnicity, particularly using longitudinal data. This study investigates the relationship between financial strain and multiple dimensions of sleep, including sleep quality, sleep disturbance, daytime dysfunction, sleep latency, and sleep medication use, across White, Black, Mixed, Asian, and Other racial-ethnic groups.</p> Methods <p>Data were drawn from Waves 4, 7, 10, and 13 of the UK Household Longitudinal Study (<i>N</i> = 36,544 individuals; 114,164 person-years). Fixed-effects regression models were applied to assess within-person changes over time.</p> Results <p>Financial strain was associated with poorer outcomes across all sleep dimensions. These associations varied by race-ethnicity: they were stronger among Asian individuals than among their White counterparts. Further disaggregation revealed that this pattern was particularly pronounced among Pakistani individuals but not among other Asian subgroups.</p> Conclusions <p>By revealing subgroup-specific disparities, particularly among Pakistani individuals, this study underscores the importance of tailoring public health strategies to address the combined effects of financial strain and racial-ethnic identity, thereby advancing equity in sleep health and overall well-being.</p>