Introduction Metabolic acidosis (MA) may accelerate the progression of chronic kidney disease (CKD) and is an important risk factor for increased mortality in CKD patients. The clinical value of MA in kidney transplant (KTx) recipients has not been extensively studied so far. Objectives The aim of this clinical single‑‑center case‑‑control study was to assess the prevalence of MA in KTx recipients in comparison with CKD patients and to identify pathogenic factors for MA in KTx recipients. Patients and methods Venous blood concentrations of bicarbonate (HCO3-) and blood hemoglobin concentrations were measured in 500 KTx recipients and 500 CKD patients matched for sex, age, and estimated glomerular filtration rate (eGFR). None of these patients received alkali treatment before the study. MA was diagnosed in KTx recipients with HCO3- levels lower than 22 mmol/l. Results The prevalence of MA was lower in KTx recipients than in CKD patients (12.0% vs 19.6%; P = 0.001). In both groups, the prevalence increased with progression of CKD stages (P <0.001 for trend) and was higher in patients with anemia. In a multivariable analysis, hemoglobin concentrations correlated independently with eGFR and HCO3- in KTx recipients (β = 0.314, P <0.001 and β = 0.274, P <0.001, respectively). Similar correlations were observed in CKD patients (β = 0.273, P <0.001 and β = 0.123, P = 0.006, respectively). Conclusions Our study revealed that the prevalence of MA is lower in KTx recipients than in CKD patients. Moreover, in KTx recipients, blood bicarbonate concentrations are related to kidney function and blood hemoglobin concentrations.