This study was carried out with the objectives to test the differences in the haemodynamic characteristics of the prostatic artery in normal and benign prostatic hyperplasia (BPH)–affected dogs using Doppler ultrasonography. In sixteen male German shepherd dogs, prostatic volume was detected and prostatic biopsy was performed. The prostatic artery blood flow parameters determined were as follows: peak systolic velocity (PSV), end diastolic velocity (EDV), Resistive Index (RI) and Pulsatility Index. The power Doppler mode was used for colour flow mapping of the prostatic artery. In PW mode at marginal locations, the waveforms recorded showed a continuous pattern typical of the high-resistance vessels, while in subcapsular locations, the waveforms recorded were continuous characteristic of the low-resistance vessel. Peak systolic velocity and EDV in both locations were significantly higher in BPH group (p < 0.001) than normal group (p < 0.05). Pixel number in BPH group in both locations was significantly higher (p < 0.05) compared to the normal group. This study shows that Doppler ultrasonography represents a valid and non-invasive method for the characterization of the blood flow in the prostatic artery in dogs affected with BPH. Moreover, statistically significant differences of blood flow velocities in prostatic artery in normal and BPH-affected dogs were detected. The RI was not able to differentiate normal dogs from dogs affected by BPH and therefore is not a parameter usable for diagnostic purposes, while Power Doppler could represent an additional diagnostic tool.