Water retention curve (WRC) is a nonlinear function that describes the relationship between the matric suction (ψ) and water content (θ) of a porous material evaluated under unsaturated conditions. WRC contains fundamental information about hydro-mechanical behavior of unsaturated porous materials of different composition. In this context, this paper presents the laboratory results and procedures used to determine the WRC of a soil-cement composite material used in road pavement construction. With this purpose, water content and matric suction measurements in a soil-cement composite with 3.5% of Portland cement by using pressure cells were developed. Fitting values of the WRC were calculated according to the theoretical four-parameter van Genuchten model. Hence, the best fit parameters of the van Genuchten water retention curve were estimated using a nonlinear fitting approach based in minimizing the sum of squared-error in nonlinear functions. Results show that the water retention curve and its parameters according to the van Genuchten model determined in this study can be used as reference values of the unsaturated parameters of soil-cement composite material used in road pavement construction. Moreover, soil-cement water retention curve shown in this study corresponds to one of the first results published in the literature on this composite material.