This study looks into the influence of matric suction on the volume change of gypsum sand soil in unsaturated conditions. The specimens were collected from Al-Najaf, Iraq, and included 14 and 29% gypsum. Three series of initial stress laboratory tests were utilized in a modified oedometer device. For each gypsum content, twelve remolded specimens were examined in unsaturated circumstances with the initial stress and applied stress using four matrices suction (30 kPa, 18 kPa, 9 kPa, and saturated state). Three tests were performed for each matric suctions with initial stresses, no initial load, 56 and 112 kPa, respectively. The findings exhibit a clear pattern of increase in the vertical strain as gypsum content rises and matric suction reduces under a variety of situations. The wetting process softens the gypsum components, which are significantly resulting in an increase in vertical strains.