The impact of exercise on the levels of endothelial progenitor cells (EPCs), a marker of endothelial repair and angiogenesis, and circulating endothelial cells (CECs), an indicator of endothelial damage, in heart failure patients is largely unknown. This study aims to evaluate the effects of a single exercise bout on the circulating levels of EPCs and CECs in heart failure patients. Thirteen patients with heart failure underwent a symptom-limited maximal cardiopulmonary exercise test to assess exercise capacity. Before and after exercise testing, blood samples were collected to quantify EPCs and CECs by flow cytometry. The circulating levels of both cells were also compared to the resting levels of 13 volunteers (age-matched group). The maximal exercise bout increased the levels of EPCs by 0.5% [95% Confidence Interval, 0.07 to 0.93%], from 4.2 × 10−3 ± 1.5 × 10−3% to 4.7 × 10−3 ± 1.8 × 10−3% (p = 0.02). No changes were observed in the levels of CECs. At baseline, HF patients presented reduced levels of EPCs compared to the age-matched group (p = 0.03), but the exercise bout enhanced circulating EPCs to a level comparable to the age-matched group (4.7 × 10−3 ± 1.8 × 10−3% vs. 5.4 × 10−3 ± 1.7 × 10−3%, respectively, p = 0.14). An acute bout of exercise improves the potential of endothelial repair and angiogenesis capacity by increasing the circulating levels of EPCs in patients with heart failure.