Abstract: An adjustable pet raincoat and a method of using the raincoat are disclosed. An adjustable pet raincoat comprises one or more foldable torso covers and an inflatable head cover. Each torso cover has one or more sections and can be fully extended or folded. A torso cover can also be attached to another torso cover to form a bigger one to fit the size of a pet. Torso straps and a chest strap are attached to torso covers and used to anchor the pet raincoat on a pet. In a further embodiment, sections of a torso cover are connected to their neighboring sections only at their middle part of divided lines to allow flexible use of each section.