A dual cartridge caulking gun adapted to mount a caulking gun caddy for expelling and dispensing material filled in the caddy, the caddy having a first tubular barrel and a second tubular barrel juxtaposed and coupled with the first tubular barrel in a longitudinal direction, said dual cartridge caulking gun comprising: a gun body; a receptacle mounted on a side of said gun body, and having an accommodation space for receiving and supporting the caddy, and at least one arcuate surface which faces said accommodation space; a plunger unit mounted within and movable relative to said receptacle in the longitudinal direction, said plunger unit including a first plunger which is actuated by a triggering action, and a second plunger which is movable with said first plunger, said second plunger being elongated along a central line parallel to the longitudinal direction; and a trigger unit mounted on said gun body and operable to drive movement of said plunger unit in the longitudinal direction toward said accommodation space, characterized by: an adjusting unit pivotably mounted on said receptacle to be movable along said arcuate surface, and having an arcuate first wall surface segment and an arcuate second wall surface segment which are angularly spaced apart from each other and which face the central line, said adjusting unit being turnable relative to said receptacle between a first supporting position, where a curvature center of said first wall surface segment meets the central line, and a second supporting position, where a curvature center of said second wall surface segment meets the central line, a distance between said first wall surface segment and the central line in the first supporting position being larger than a distance between said second wall surface segment and the central line in the second supporting position. a gun body; a receptacle mounted on a side of said gun body, and having an accommodation space for receiving and supporting the caddy, and at least one arcuate surface which faces said accommodation space; a plunger unit mounted within and movable relative to said receptacle in the longitudinal direction, said plunger unit including a first plunger which is actuated by a triggering action, and a second plunger which is movable with said first plunger, said second plunger being elongated along a central line parallel to the longitudinal direction; and a trigger unit mounted on said gun body and operable to drive movement of said plunger unit in the longitudinal direction toward said accommodation space, characterized by: an adjusting unit pivotably mounted on said receptacle to be movable along said arcuate surface, and having an arcuate first wall surface segment and an arcuate second wall surface segment which are angularly spaced apart from each other and which face the central line, said adjusting unit being turnable relative to said receptacle between a first supporting position, where a curvature center of said first wall surface segment meets the central line, and a second supporting position, where a curvature center of said second wall surface segment meets the central line, a distance between said first wall surface segment and the central line in the first supporting position being larger than a distance between said second wall surface segment and the central line in the second supporting position.