A guardrail mounting bracket for a staircase includes an upper clamping bracket comprising an upper post engagement portion and an upper stair engagement portion, the upper stair engagement portion defining an upper stair engagement surface; a lower clamping bracket comprising a lower post engagement portion and a lower stair engagement portion, the lower stair engagement portion defining a lower stair engagement surface; and a front clamping bracket coupled to the lower clamping bracket and defining a front stair engagement portion.