ABSTRACT Platelet-rich plasma (PRP) has been proposed as an agent to accelerate the healing process and stimulate the regenerative capacity of tissues due to its abundance of growth factors. A large variety of kits and protocols are available to obtain PRP by different cell-separation systems. However, the lack of standardization may lead to inconsistent results. The aim of this study was to characterize cellular composition, platelet parameters using the ADVIA 120 flow cytometer, and TGF-β1 concentration from the PRP product obtained through a closed system, using simple centrifugation. Six clinically healthy horses were used in this study. The protocol in the closed system resulted in approximately 1.6-fold higher platelet and approximately 2.0-fold lower white blood cell concentrations in comparison with whole blood values. The evaluated system was efficient in concentrating platelets and in retrieving a small number of leukocytes, using a protocol of single centrifugation at low speed.