The use of chemical scale inhibitors in the oil and gas industry for subsea installations has been presented for a long time, but the ever-increasing exploration of HPHT (high pressure high temperature) wells put demands on knowledge of how the rheological properties such as viscosity of scale inhibitors behave under large pressures. This work reports new experimental data of high-pressure viscosity using a rotational rheometer, measured across a pressure range of 0.1 MPa to 15 MPa, at temperatures from 273 K to 298 K, and a broad range of shear rates, 100 $$s^{-1}$$ s - 1 to 1000 $$s^{-1}$$ s - 1 for a scale inhibitor. The experimental data are used to construct a power-law regression model with fitting parameters. Results indicate that the inhibitor shows a near Newtonian behavior.