Objectives: With sustaining pandemics, the risk of acute heart failure and acute kidney disease (AKI) in COVID-19 patients has already been sufficiently invested. However, research on the cardio-renal axis is insufficient.  Methods: We performed a retrospective cohort study in a dedicated COVID-19 hospital (Bagae hospital) from December 2020 to July 2021. Baseline renal function was defined as the lowest value among serum creatinine performed during hospitalization. Multivariate logistic regression was used to measure the association of cardiac biomarkers (brain natriuretic peptide [BNP], troponin I [TnI], and creatine kinase-MB [CK-MB]) and outcomes (In-hospital mortality and acute kidney injury [AKI]).  Results: Of the 964 patients, 44 were stage 3 or higher chronic kidney disease patients and 126 were end-stage renal disease (ESRD) patients. The overall in-hospital rate of mortality was 11.5 % (111/964 patients) and AKI was 32.4% (272/840 patients). ESRD patients had highest level of serum BNP than other groups (60ml/min/1.732≤eGFR: 41.4±97.5 pg/mL; eGFR<60ml/min/1.732: 246.4±753.9 pg/mL; ESRD: 852.2±1240.1 pg/mL; p-value <0.001). In univariate analysis elevated levels of serum BNP, TnI and CK-MB were associated with increased risk of in-hospital mortality and AKI, especially in patients whose 60ml/min/1.732≤eGFR (Table 1). In multivariate analysis, elevated serum BNP was associated with increased risk of in-hospital mortality (Odd ratio [OR] 2.09, confidential interval [CI] 1.017–4.281, p-value 0.044) and AKI occurrence (OR 3.47, CI 1.781–6.947 p-value <0.001) in patients whose 60ml/min/1.732≤eGFR (Figure 1). Elevated serum TnI and CK-MB were associated with increased risk of in-hospital mortality (TnI, OR 2.54, CI 1.093–5.819, p-value 0.028; CK-MB, OR 3.58, CI 1.639–7.738, p-value = 0.001).  Conclusions: Elevated serum cardiac markers (BNP, TnI, and CK-MB) were associated with increased in-hospital mortality in COVID-19 patients. Among them, elevated serum BNP was associated with an increased risk of AKI.