Abstract: Disclosed is a C-clamp having dual fastening mechanism. Pivoting a pivotal handle about a fixed handle will cause a pin to contact and move a spring biased first fastening member to a slanted position, move a pawl backward along a ratchet, and move an abutment member to vertically dispose a second fastening member by urging against a resilient member, thereby fastening a shaft by both the first and second fastening members since the second fastening member is slanted immediately after releasing the pivotal handle, and stepwise fastening an object. Instead, pressing a quick release will disengage the pawl from the ratchet so as to pivot the pivotal handle to return the second fastening member to a vertical position through activation of the abutment member, and return the first fastening member to a slanted position, thereby enabling a removal of the object.