Dynamic viscosities of seven (0.3207, 0.6771, 1.5235, 2.0310, 2.6118, 3.2810, and 4.0628) mol‚kg -1 and kinematic viscosities of two (4.9861 and 6.0941) mol‚kg -1 aqueous Ca(NO 3 ) 2 solutions have been measured in the liquid phase with a capillary flow technique. Measurements were made at six isobars (0.1, 5, 10, 20, 30, and 40) MPa. The range of temperatures was from (298 to 573) K. The total uncertainty of viscosity, pressure, temperature, and concentration measurements were estimated to be less than 1.5%, 0.05%, 15 mK, and 0.014%, respectively. The reliability and accuracy of the experimental method was confirmed with measurements on pure water for five selected isobars (1, 10, 20, 40, and 50) MPa and at temperatures between (294.5 and 597.6) K. The experimental and calculated values from International Association for the Properties of Water and Steam formulation for the viscosity of pure water show excellent agreement within their experimental uncertainty (average absolute deviation, AAD ) 0.27%). A correlation equation for viscosity of solutions was obtained as a function of temperature and pressure for each measured composition by a least-squares method from the experimental data. The AAD between measured and calculated values from this correlation equation for the viscosity was 0.6 %. The measured values of viscosity at atmospheric pressure were directly compared with the data reported in the literature by other authors.