Objective To explore the correlation between serum high density lipoprotein (HDL) levels and cognitive function in patients with bipolar disorder. Methods A total of 99 patients with bipolar disorder were enrolled from the inpatient of Suzhou Guangji Hospital.Serum HDL levels were measured by enzymatic colourimetry.Cognitive function was assessed by the repeatable battery for the assessment of neuropsychological status (RBANS). The relationship between serum high density lipoprotein and cognitive function was analyzed by correlation analysis and stepwise multiple regression analysis. Results Serum HDL levels ((1.39±0.55)mmol/L)were positively correlated with the RBANS total score (68.92±12.48)(r=0.238, P=0.034) and language score(80.59±15.97) (r=0.239, P=0.033) in patients with bipolar disorder.Stepwise multiple regression analysis showed that serum HDL level was the influencing factor of total score of RBANS(β=4.791, t=2.151, P=0.035)and speech function(β=7.363, t=2.247, P=0.027). Conclusion Serum HDL levels can influence cognitive function, especially speech function in patients with bipolar disorder. Key words: High density lipoprotein; Bipolar disorder; Cognition