A dust cup, a dust cup assemble and a handheld cleaner are provided and the dust cup for the cleaner having the negative pressure device comprises a base and a cup casing, wherein the cup casing has a non-closed annular cross section with an opening so as to define a dust collecting chamber having a non-closed annular cross section in the cup casing, the cup casing is disposed at a top of the base, a mounting space located outside the dust collecting chamber is defined between an inner-ring wall face of the cup casing and a top wall of the base, a top of the mounting space is directly opened, and a side of the mounting space is opened by an opening, and the negative pressure device is mounted to the mounting space via an opened portion of the mounting space.