Objective To explore the correlation between mindfulness level and sleep quality of cancer patients. Methods By convenience sampling, 150 patients hospitalized in a cancer hospital in He'nan province from June to August 2016 were selected and surveyed by mindful attention awareness scale (MAAS) and Pittsburgh sleep quality index (PSQI). Results A total of 146 questionnaires were retrieved. Average scores of the research objects in MAAS were (60.44±12.19), and PSQI scores in all dimensions and total score were all higher than domestic norm (P<0.05). Incidence rate of sleep disorder was 51%. It was shown in Pearson correlation analysis that sleep duration, sleep disorder, daytime functional disorder and total score in PSQI were negatively related with mindfulness level (P<0.05). Conclusions Sleep quality of cancer patients is poor. The higher mindfulness level is, the higher sleep quality is. Medical staff can help the patients improve their sleep quality by improving their mindfulness level.