Three structural self-tapping screws with diameters of 6~10 mm and lengths of 267~302 mm were used as fasteners. Four wood species of Japanese cedar, Douglas fir, southern pine, and Kapur were used for making heterogeneous-grade structural glulam members in the study. Three glulam members were assembled with structural self-tapping screws as a joint to investigate the double-shear properties of a connection subjected to a load. Results indicated that the maximum shear capacity of a connection assembled with Kapur glulam members was 19.9, 54.7, and 48.5%, respectively, higher than those of Douglas fir, southern pine, and Japanese cedar glulam connections. The maximum shear capacity of a double-shear connection loaded perpendicular to wood grain was 16.0% higher than that loaded parallel to the wood grain. In the case of a glulam joint assembled with an aluminum connector, the maximum shear capacity of a double-shear connection assembled with Kapur glulam members was 20.1, 31.8, and 34.3%, respectively, higher than those of Douglas fir, southern pine, and Japanese cedar glulam connections. The maximum shear capacity of a double-shear connection loaded perpendicular to the wood grain was 19.5% higher than that loaded parallel to the wood grain. Further, the maximum shear capacity of a double-shear connection assembled with 8-mm structural self-tapping screws and an aluminum connector was 45.5% higher than that of a wood-wood connection. The maximum shear capacity of a double-shear connection assembled with 8- and 10-mm diameters of structural self-tapping screws were 46.8 and 92.3%, respectively, higher than those with 6-mm diameter screws. The tendency for energy dissipation of the connection subjected to a shear load was similar to that of the maximum shear capacity. The calculated results of the allowable joint strength for self-tapping screws showed a tendency of underestimation when the allowable shear calculations for both wood screws and lag screws in the wood-frame structure design code were applied.