Abstract: A downspout flow diverter for diverting water from a gutter downspout to an alternate location outside the downspout. A first embodiment of the downspout flow diverter comprising a diverter plate pivotally supported from a main body, and a sliding jacket disposed for sliding engagement with the main body, wherein the position of the diverter plate is responsive to the position of the sliding jacket. The first embodiment of the downspout flow diverter further comprising a seepage barrier, defining a drain void, for channeling water seepage from around the stowed diverter plate, back into the main body.