Our objective was to investigate the impact of low-intensity aerobic training on cognitive functions in severely deconditioned subacute and chronic stroke patients. For this purpose, a randomized, controlled pilot study was designed involving subacute and chronic stroke patients. Thirty-seven eligible patients participated in the 4-week-long randomized, controlled pilot study. Patients were randomized into study group and control group and both groups participated in conventional physiotherapy included occupational therapy. Only the study group's patients participated in a low-intensity aerobic training by cycle ergometer. Cognitive evaluations (Functional Independence Measure Cognitive part - FIM-cog; Coding and Symbol Search tasks of the Processing Speed index and Digit Span task of Working Memory index of Wechsler Adult Intelligence Scale-Fourth Edition) were performed before and after the programme. In-group analysis showed a significant improvement in study group patients regarding Coding subtest of Processing Speed domain (P = 0.003). Symbol Search subtest of Processing Speed showed significant improvements in both groups by the end of the programme (study group, P = 0.041; control group, P = 0.006). There were no significant changes in the FIM-cog and Digit Span task. The intergroup analysis did not find significant difference between the two groups. It was concluded that even the low-intensity aerobic training may improve special domains of cognitive function after stroke. Further studies are needed to confirm the impact of low-intensity aerobic training on cognitive functions.