Cancer patients frequently encounter difficulties associated with suboptimal sleep quality. Bright Light Therapy (BLT), an innovative treatment approach, has shown promise in enhancing sleep quality. However, several literature reviews showed conflicting results, and more analysis should be conducted regarding detailed BLT settings on sleep. This meta-analysis was undertaken to comprehensively assess the impact of BLT on sleep quality among cancer patients. Twelve studies with 679 patients were included. Compared with the control group, BLT overall resulted in significant improvements in terms of sleep quality [g = −0.34], total sleep time [g = 0.24], wake after sleep onset [g = −0.80], and fatigue [g = −0.54]. However, it did not yield a statistically significant effect on sleep efficiency, sleep onset latency, and insomnia severity. Regarding light settings, interventions featuring light intensities >5000lux, intervention duration ≥4 weeks, spectral emission peak at 464∼465 nm, and using a lightbox demonstrated heightened efficacy in improving sleep. BLT may be considered a supplementary therapeutic option to improve sleep quality among cancer patients. However, more extensive and rigorous studies are necessary to determine the optimal timing of BLT delivery and its applicability to cancer patients across different age groups.