Most natural coastal environments comprise heterogeneous sediments, such as sand mixtures. To predict the wave-driven sand transport in these environments, coastal engineers have developed practical formulae which, due to a lack of laboratory experiments with sand mixture, are parametrised using insight and quantitative data obtained from experiments with well-sorted (or single-size) sands. Therefore, the purpose of this work was to gather new insight into the wave-driven transport of sand mixtures, and to use it to test the capability of a practical formula. Experiments with several sand mixtures and velocity-skewed oscillatory flows were conducted in both oscillatory flow tunnel and wave flume. Measurements of net transport rate, per size fraction, were obtained for sand mixtures in the ripple and in the sheet-flow regime of transport. Net transport rates data show effects of the interaction between size fractions, and that small variations in bed composition (25%) may reduce the net transport rate magnitude or even change its direction. Time- and height-dependent velocity and concentration measurements were used to obtain sand fluxes for mixtures in sheet-flow. Analysis of the sand fluxes reveals the underlying sand transport processes, which show that unsteady effects are dominant for mixtures with percentages of fine sand larger than 50% and energetic flows. The net transport rate data are used to test the capability of a practical sand transport formula to predict correct net total and fractional transport rates for sand mixtures. The formula predicts net total transport rates well for most of the sand mixtures, with better prediction for high-velocity flows than for low-velocity flows.