This experimental database aimed to obtain the pressure and void fraction wave velocities in air-water slug flow in horizontal orientation. The database contains the raw pressure and dual impedance probe data in a fully instrumented test section. One hundred repetitions for each pair of superficial velocities were performed to filter the intrinsic transient nature of slug flow, especially to obtain the void fraction signal. The test grid encompasses the liquid and gas compression and expansion, i.e., decrease or increase in the liquid or gas superficial velocity. The superficial velocities of liquid and gas gases varied from 0.30 m/s to 0.60 m/s.