Mechanical properties such as bulk modulus, shear modulus, and failure stress of rootzone sand mixtures are some of the key parameters in understanding the load-response of sands used in professional golf courses. According to the United States Golf Association (USGA) specifications, appropriate particle size distributions and their shape are important for preparing putting greens and bunker sands. Despite being an important parameter, the influence of sand particle shape on the bulk mechanical properties of the rootzone mixtures has not been studied systematically using a fundamental tester. Toward this end, bulk mechanical properties were measured using a lowpressure cubical (true) triaxial tester. In this study, four of the commonly used basic shapes, i.e., round, subround, subangular, and angular sand particles comprising rootzone mixtures with sphagnum peat (organics) were tested at two different moisture levels, airdried and 30 cm moisture tension conditions. For all rootzone sand mixtures, an increase in bulk modulus was observed with increasing isotropic pressure. The failure stress values increased with the increase in mean pressure for air dried samples. In general, moisture increased compressibility of sands and decreased failure strength and shear modulus values. Peat had a dominant influence on the mechanical response of all four sand shapes. When peat and moisture were added, the rootzone mixture became most compressible and easier to fail, with noticeable changes in bulk mechanical properties.