Objective To explore the correlation between sleep quality and cognitive function in schizophrenia patients with metabolic syndrome （MS）. Methods A total of 86 patients with schizophrenia admitted to the Shandong Mental Health Center from January 2023 to January 2024 were selected as participants. According to the presence of MS， patients were divided into MS group （34 cases） and non-MS group （52 cases）， and 47 healthy individuals recruited from the Lixia District Community， Jinan City， Shandong Province during the same period were included as healthy control group. The Positive and Negative Syndrome Scale （PANSS） was used to assess the severity of symptoms in patients with schizophrenia. Pittsburgh Sleep Quality Index （PSQI） was used to evaluate the subjective sleep quality of patients， and a sleep monitor was used to evaluate the objective sleep quality. The cognitive function of patients was evaluated using the Part A and B of the Trail Making Test， Digit Symbol Substitution Test， Animal Naming Fluency Test， and Digit Span Test （forward and backward）. Spearman correlation was used to analyze the correlation between subjective and objective sleep quality and cognitive function in MS patients. Results Patients in MS group had a shorter total sleep time ［363.75 （288.13， 420.75） minutes］ compared to non-MS group ［427.75 （349.88，472.63） minutes］ （Z= -2.615， P=0.009）， lower average oxygen saturation ［95.00 （94.00， 96.00）%］ than non-MS group ［96.00 （95.00， 97.00）%］ （Z=-3.296， P=0.001）， higher apnea hypopnea index ［2.70 （1.58， 7.93） times/h］ than non-MS group ［1.30 （0.40， 4.30） times/h］ （Z=-2.191， P=0.028）， and shorter rapid eye movement sleep duration ［（77.25±21.81） minutes］ than non-MS group ［（88.46±26.74） min］ （t=-2.040，P=0.045）， and the differences were statistically significant. The total score of the PSQI in MS group （9.12±3.66） was higher than that in non-MS group （7.44±3.69） （t=2.065， P=0.042）. Among the factor scores of the PSQI， the sleep quality score ［1.00 （1.00， 2.00） points］ was higher than that of non-MS group ［1.00 （0， 1.00） points］ （Z=-2.537，P=0.011）， and the above differences were statistically significant. There was no statistically significant difference in the scores of other subjective and objective sleep indicators and cognitive function （P ＞ 0.05）. Spearman correlation showed that in MS group， the average oxygen saturation was positively correlated with the score of Digit Symbol Substitution Test （rs=0.355， P=0.039）， the score of the hypnotic drug in the PSQI scale was negatively correlated with Animal Naming Fluency Test scores （rs=-0.447， P=0.008）， the score of the sleep latency was negatively correlated with HDL-C （rs=-0.339， P=0.050）， the score of the sleep quality was negatively correlated with HDL-C （rs=-0.375， P=0.029）， the score of fasting blood glucose was negatively correlated with the score of the Digit Span Forward Test （forward） （rs=-0.431， P=0.011）， and the total score of Positive and Negative Syndrome Scale （PANSS） was positively correlated with the duration of the Trail Making Test B （rs=0.583，P ＜ 0.001）. Conclusions Schizophrenia patients with MS have differences in subjective and objective sleep quality， and there is a certain correlation between subjective and objective sleep quality and cognitive function and metabolic indicators. This suggests that clinicians should pay attention to the influence of MS in the diagnosis and treatment of schizophrenia