Objective To explore the associations among benefit finding, rumination and sleep quality of elderly patients with lung cancer. Methods A total of 225 lung cancer elderly patients were investigated by using the Pittsburgh Sleep Quality Index, Benefit Finding Scale, and Ruminative Response Scale. Results The sample scored 9.02±3.11 on sleep quality, 43.23±7.43 on benefit finding, and 43.66±8.79 on rumination. Structural equation model revealed that benefit finding had direct and indirect effect on sleep quality (β=-0.234,-0.026;P＜0.05 for both); rumination had a direct effect on sleep quality (β=0.367,P＜0.05). Conclusion Elderly patients with lung cancer report poor sleep quality and medium level of benefit finding.Benefit finding can ameliorate sleep quality, whereas rumination deteriorates sleep quality and plays a negative mediating role in benefit finding and sleep quality.