Stabilization of soil using cement can increase the bearing capacity, compaction, and strength characteristics. However, limited research has been done on cemented clayey sand, and there is a lack of knowledge of the combined effect of the clay and cement content on the strength and deformability characteristics of mixed soil. In the present study, two soil mixtures were prepared: (1) Soil A consists of 80% sand and 20% clay, and (2) Soil B consists of 60% sand and 40% clay. The prepared mixtures were stabilized by Portland cement at target ratios of 1%, 2% and 3% by dry weight, and they were cured for 7, 14, and 28 days. A series of unconfined compression tests were performed on the untreated and cement-treated specimens. There was a continuous increase in the unconfined compressive strength (UCS) with the increase in cement content, clay content or curing period. The deformability index rose with the growth of the clay content, but it decreased over time with increasing the curing period. Two empirical equations have been developed on the basis of the cement and clay contents to predict the UCS of cemented clayey sand at any curing time (≤ 28 days).