A water jet propulsion watercraft includes a hull having a sealed engine room, an engine installed in the engine room, a jet propulsion unit arranged to be driven by the engine so as to suck in water from around the hull and jet the water, a saddle type seat disposed above the engine room, a first exhaust pipe, an exhaust pipe cooling unit, and a catalyst unit. The first exhaust pipe is attached to a side of the engine inside the engine room, extends rearward from the side of the engine, and is arranged to guide exhaust gas discharged from the engine. The exhaust pipe cooling unit is arranged to cool the first exhaust pipe. The catalyst unit is connected to the first exhaust pipe, is disposed inside the engine room so as to oppose a rear surface of the engine, and is arranged to promote reaction of components contained in the exhaust gas.