This paper presents the effect of weathering conditions on unconfined compressive characteristics of compacted sand mixed with recycled bassanite that was derived from waste plasterboard. The weathering conditions in this paper referred to wetting and drying repetitions. Sand-bassanite mixtures compacted at optimum water content and at water content of dry of optimum, were cured for 28 days. The strengths of cured sand-bassanite mixtures were determined by unconfined compression tests after 0,1, and 3 wetting and drying repetitions. The effects of wetting and drying repetitions on stress-strain behavior of compacted sand-bassanite mixtures are quantified. As a result, for sand-bassanite mixtures compacted at optimum water content, the unconfined compressive strength of mixtures with wetting and drying repetitions is little changed from those without repetitions. For sand-bassanite mixtures compacted at water content of dry of optimum, however, the unconfined compressive strength of mixtures with wetting and drying repetitions becomes about 90% of those without repetitions. The first cycle of wetting and drying repetitions decreases the unconfined compressive strengths of compacted sand-bassanite mixtures by 5-10%, but further repetitions hardly decrease them.