A trash bag holder and expanding form is made from a sheet of stiff material that has at least three panels to hold a bag in an erect condition and to expand the opening of the bag into a shape that will allow the user to fill the bag with leaves or trash without having to hold the bag. The panels are separated by parallel, vertically disposed score lines that act as fold lines or hinges between the panels of the holder. The holder can be formed from high density corrugated polyurethylene (HDPE) board, recycled plastic corrugated board that may have a lap joint sealed by a sonic weld. The panels are proportioned so that the sheet material can be folded flat with the panels lying against one another. When the invention is folded into its operational configuration, the score lines act as corners such that the form is tubular or U-shaped with open ends and braces may hold panels in extended opposing relationship.