Objective: We evaluated the effects of a specialised oral nutritional supplement (ONS) containing arginine and proline, with high vitamin A, C and E, zinc and selenium content, on the repair of hard-to-heal wounds. Method: Patients with hard-to-heal wounds were evaluated at five timepoints (S0–S4) over four consecutive weeks. At S0 patients were randomised to the specialised ONS (n=15; 25 wounds) or control (n=15; 25 wounds) groups. Posology was 200ml twice daily over the research period. Wound surface area and perimeter were monitored. In addition to the metric data, it was also possible to calculate the rate of wound contraction and the linear growth of the wound edges, looking for wound-healing predictive factors. Results: A total of 30 patients took part in the study. Mean age was 65 years and 50% of patients had diabetes. Of the total evaluated wounds, 78% were <50cm2, 14% were 50–150cm2 and 8% were >250cm2. In 96% of cases, the wounds were in the lower limbs. A statistically significant reduction (p=0.004) in surface area of the wounds due to the specialised ONS, with a performance peak between S1 and S2, was observed. This specialised ONS did not induce changes in blood pressure, blood glucose level or renal function. A mean weekly wound edge growth of 1.85mm in patients with diabetes and 3.0mm in those without diabetes was observed. These results were 2.9 and 4.6 times, respectively, higher than expected, according to the literature. Conclusion: Specialised ONS can be a therapeutic option for hard-to-heal wounds.