This research investigates the shear modulus and damping of cemented sand through laboratory tests with flush mounted transducers, bender element and resonant column devices. The effect that the cement type, cement content, void ratio, confining pressure and sand particle properties have on the reduction of shear modulus and increase in damping with increasing shear strain as well as the maximum shear modulus are examined through the test results. A new formulation modeling the nonlinearity of the stiffness of cemented sand is proposed and evaluated with the data from this and previous studies. Model parameters are determined for different types of sand and cementation agents. This research advances the understanding of cemented sands by providing a database of test results, and a model which can be used to predict the response of cemented sand to dynamic loads. This can be useful for performing site response analysis for naturally cemented sites or sites that have been improved by cementation.