Abstract Background Cardiorespiratory fitness seems to play an important role in the general health of patients undergoing hemodialysis (HD). However, the prediction of peak oxygen uptake (V̇O 2peak ) in a clinical setting is not widely adopted for these patients. Objectives Evaluate the agreement and reliability between directly and indirectly V̇O 2peak measurements in patients undergoing HD. Methods This is a cross-sectional study with patients undergoing HD that performed a cardiopulmonary exercise test (CPET) with 5/10 watts incremental load in each minute using a cycle ergometry to directly evaluate the V̇O 2peak , and the 6-min walk test (6MWT) in a 30-m corridor to indirect measures it. Both tests were performed on a midweek non-dialysis day. Bland–Altman analysis of agreement limits was used with direct and indirect V̇O 2peak values. Intraclass correlation coefficient (ICC) and Cronbach’s Alpha was used to evaluate the reproducibility and reliability between direct and indirect V̇O 2peak values. Results Twenty-six patients (54.4 ± 14.5 years, 53.8% of male) were evaluated. The V̇O 2peak direct mean obtained through CPET was 15.91 ± 5.26 (ml/kg/min), while the indirect mean obtained through 6MWT was V̇O 2peak of 14.89 ± 4.21 (ml/kg/min). There was a strong positive correlation between both V̇O 2peak values ( r  = 0.734; p  < 0.001). The Bland–Altman analysis demonstrated that the methods agreed with each other ( p  = 0.103). Also, the ICC (0.829) and Cronbach's Alpha (0.846) showed excellent reproducibility and reliability. Conclusions 6MWT is a reliable tool for estimating V̇O 2peak in patients undergoing HD.