A latching mechanism is applied to be mounted on a webbing of a seat belt system. The latching mechanism has a tongue assembly and a slider mounted on the tongue assembly. The slider has a bridge located at a side of the tongue assembly. The webbing passes through a bottom end of the bridge and is inserted through the slider and the tongue assembly. The webbing has a shoulder belt located at a side, which has the bridge, of the latching mechanism. When the slider is located in an unlocked position, the latching mechanism is capable of freely moving along the webbing. A tension of the shoulder belt acts on the bridge for driving the slider to move from the unlocked position to a locked position, such that the webbing is clamped and locked by the slider and the tongue assembly.