Bending moment resistances of L-shaped joints connected with two gusset plates stapled on one side of joint members in oriented strandboard (OSB) were investigated. Factors were joint member material type, rail width, and number of staples. Experimental results showed that ultimate moment resistances of L-shaped, gusset-plate joints ranged from 429 to 842 N-m. Ultimate moment resistance loads of joints connected with 12 staples were 43% higher than those with 8 staples. Ultimate moment resistance loads increased as rail width increased from 152 to 203 mm with an increment of 25.4 mm, but the significance was affected by material type and number of staples. The increase in ultimate moment resistance loads of L-shaped, gusset-plate joints was not sensitive to material density profile change and density increase when 178-mm-wide or less rails were used, but the increase in moment resistances was sensitive to density increase when 203-mm-wide rails were used. Moment load-displacement curves of gusset-plate joints indicated that moment resistance loads at the ultimate point were two times their corresponding moment resistance loads at a proportional limit. The mechanical model was verified experimentally as a valid means for deriving estimation equations of moment resistances of L-shaped, gusset-plate joints in OSB.