The density (rho) and viscosity (mu) of aqueous (piperazine (PZ) + carbon dioxide (CO(2))) solutions were measured over a temperature range of (293.15 to 333.15) K and concentration ranges of (1.5 to 7.0) mol.kg(-1) PZ ((2 to 20) molal (m) PZ) and (0 to 4.0) mol.kg(-1) CO(2). Data for density and viscosity are presented in tabular form and include units useful for CO(2) capture applications (CO(2) loading and PZ concentration in m). Density data are analyzed as the ratio of rho to the density of water to eliminate the effect of temperature. On this basis, rho for (5 to 12) m PZ ((3.2 to 5.0) mol.kg(-1) PZ) was correlated with a linear regression as a function of CO(2) and PZ concentrations to within 0.78% for all data. A prediction of rho up to 20 m PZ induces an error of only 1.5 %. Viscosity data are analyzed in a similar way, and a regression for 8 m PZ (4.1 mol.kg(-1) PZ) viscosity fit all experimental data within 6.0 %. The applicability of these regressions to online monitoring of a PZ based CO(2) capture application is discussed.