Abstract: An apparatus for sealing liquid-tight a liquid filled carton, having at its open end a cover attached to the body of the carton so as to be pressed down upon and adhesively secured to sealing flaps attached to the body of the carton at its open end, has a conveyor for bringing filled cartons into registry with carton sealing assemblies each of which includes a pair of pivotally mounted arms for firmly clasping the carton in substantially complete contacting encompassment over a portion of its length immediately below the open top, and also includes a pivotally mounted plate for pushing the cover down into contact with the sealing flaps. The paperboard of which the carton is formed is preferably coated with polyethylene, and after the carton has been firmly clasped it is transported by the conveyor past a heat source which melts the polyethylene on the areas that are to be sealed together.