Objectives: Piperacillin/tazobactam combined with vancomycin has been associated with a decline in renal function when compared with monotherapy. Teicoplanin is a glycopeptide similar to vancomycin. We investigated whether piperacillin/tazobactam combined with teicoplanin is associated with a decline in renal function aswell. Methods: We conducted a single-centre retrospective cohort study with data from our electronic health records from 9 August 2013 to 15 November 2019, including all adult patients that received either piperacillin/tazobactam, teicoplanin or piperacillin/tazobactam ! teicoplanin. The incidence of acute kidney injury (AKI) at 48-72 h served as the primary outcome, whereas change in serumcreatinine served as a secondary outcome. Results: Of the 4202 included patients, 3188 (75.9%) received piperacillin/tazobactam, 791 (18.8%) received teicoplanin and 223 (5.3%) received piperacillin/tazobactam ! teicoplanin. The incidence of AKI at 48-72 h after commencement of antibiotic therapy was 5.4% for piperacillin/tazobactam, 3.4% for teicoplanin and 11.7% for piperacillin/tazobactam ! teicoplanin (P < 0.001). However, mean serum creatinine at 48-72 h was slightly higher in the piperacillin/tazobactam ! teicoplanin group therapy compared with baseline [!1.61% (95% CI -2.25 to 5.70)], indicating a slight decrease in renal function, and decreased for piperacillin/tazobactam [-1.98% (95% CI -2.73 to -1.22)] and teicoplanin [-8.01% (95% CI -9.54 to -6.45)]. After correcting for significant confounders in a multivariate linear regression analysis, these patterns remained. Conclusions: Our study suggests that piperacillin/tazobactam ! teicoplanin is associated with a higher prevalence of AKI compared with monotherapy. However, as the overall decline in renal function with piperacillin/ tazobactam ! teicoplanin is very small, its clinical relevance is likely limited. Therefore, piperacillin/tazobactam ! teicoplanin can probably be safely combined.