It is currently unknown whether levosimendan can improve clinical outcomes in patients undergoing cardiac surgery. This meta-analysis aimed to assess the effect of levosimendan on mortality and the duration of intensive care unit (ICU) and hospital stay in adult patients undergoing cardiac surgery. A comprehensive search for eligible articles was conducted in PubMed, OVID and Cochrane databases of clinical trials and the Web of Science from database inception to August 2017. Stata/SE 11.0 was used to calculate the pooled odds ratio for postoperative mortality and the pooled standardized mean difference (SMD) for the duration of ICU stay and hospital stay. A total of 30 randomized controlled trials were included in the final analysis; the pooled results indicated that perioperative administration of levosimendan was associated with a reduction in postoperative mortality [5.8% vs 8.5%; odds ratio 0.66, 95% confidence interval 0.50-0.86, P = 0.002; I2 = 17.1%; 25 trials; 3239 patients] and length of ICU stay (SMD -0.32, 95% CI -0.58 to 0.06, P = 0.017; I2 = 88.0%; 23 trials; 2536 patients) compared with the control group but not in length of hospital stay (SMD -0.41, 95% CI -0.89 to 0.07, P = 0.094; I2 = 95.9%; 18 trials; 2047 patients). A subanalysis was conducted for trials published after 2015, and it suggested that levosimendan could not reduce the postoperative mortality (odds ratio = 0.91, 95% CI 0.63-1.31, P = 0.626; I2 = 0.9%), length of ICU stay (SMD -0.03, 95% CI -0.32 to 0.27, P = 0.850; I2 = 81.2%) or length of hospital stay (SMD 0.06, 95%CI -0.43 to 0.54, P = 0.821; I2 = 91.3%). To summarize, the evidence from studies published in the last 3 years indicated that perioperative administration of levosimendan was not associated with better clinical outcomes in adult patients undergoing cardiac surgery.