Abstract Aims To investigate the associations of cardiorespiratory fitness with cardiac, vascular, renal and cardiorenal characteristics in chronic heart failure in a telerehabilitation randomized clinical trial. Secondly, to evaluate the associations of cardiorenal syndrome with the effects of exercise. Methods and results Sixty‐nine heart failure patients attended baseline examination, and 61 patients were randomly assigned 1:1 to 3‐month telerehabilitation or control. Data were collected at baseline and 3‐month post‐intervention, including echocardiography and vascular ultrasound, laboratory tests, exercise test with peak oxygen consumption (VO2peak) measurement and 6‐min walk test (6MWT). Baseline VO2peak and 6MWT distance was 0.85 mL*min−1*kg−1 lower and 20 m shorter per 10 mL/min/1.73m2 lower estimated glomerular filtration rate (both P 50% more common compared with those without (all P