A tool container system includes a first tool container and a second tool container. The first tool container has a first base, a first cover pivotably attached to the first base by a first hinge portion, a first base locking member coupled to the base, a first cover locking member coupled to the first cover, and a first latch coupled to the first base and moveable between a first unlocked position in which the first cover is movable relative to the first base between a closed position and an open position, and a first locked position in which the first latch engages the first cover locking member and the first cover is locked to the first base in the closed position. The second tool container is stackable on the first cover of the first tool container and having a second locking member. When the second tool container is stacked on the first tool container, the second tool container is lockable to the first tool container when the first latch is moved to the first locked position to engage both the first cover locking member and the second locking member.