We have investigated the interaction between a surface acoustic wave (SAW) and the two-dimensional electron gas formed at the interface of InSb/InAlSb heterojunctions. The samples were grown by molecular beam epitaxy on (100) SI GaAs substrates. Measurements were performed with the SAW travelling along the [110] direction, and a numerical approach was used to calculate the appropriate SAW coefficients. Along [110] a leaky SAW solution exists, with a piezoelectric coupling coefficient K2eff of 3.52 × 10−4, and velocity of 2680 m s−1. At high magnetic fields Shubnikov–de Haas-like oscillations were observed in the SAW attenuation and phase shift that reflect the oscillating magnetoresistance, and a quantitative analysis of the oscillations yields reasonable values for the electron concentrations. The best defined oscillations were observed in measurements on the sample with the lowest doping.