Backfill strength properties are the determinant factor that is first considered in an underground mining support with backfill application. Cemented rockfill (CRF) is one type of backfill that has potential compared to other types of cemented backfills because it usually has higher strength. However, the critical period for cemented rockfill is when its strength properties are still developing. Therefore, the earlier strengths rather than the 28-day strength are of interest in this experiment. Tests to understand the compressive and tensile properties of underground cemented rockfill were conducted with granite aggregate rock material retrieved from a diamond mine in Northern Canada. Two different mixtures of cemented rockfill as used in the mine were recreated and were subjected to a uniaxial compression test and split-tensile test. The tests were conducted based on seven, 14, 21 and 28 days of the specimen’s age. The result of the experimental study showed that the second mixture has 28-day compressive and split-tensile strengths, respectively, three times those of the first mixture. In simple correlation, the split-tensile strength of the first mixture and the second, respectively, ranges approximately from 12.96 to 18.07 percent and 15.41 to 17.43 percent of the corresponding compressive strength. This study formulated the better relationship between those strength properties mathematically. This model study of CRF may also be useful in the design and stability analysis of underground mining support with cemented rockfill.