Rainwater diverter comprises a base member and a sleeve member. The base member includes a tubular conduit having an upper end and a lower end sized to closely fit within an upper end of a lower downspout section. Surrounding the tubular conduit is a fluid chamber having an open upper end and a closed bottom, and a discharge opening adjacent the bottom. The sleeve member has a lower end sized to have a close sliding fit inside the open upper end of the chamber, and an upper end sized to have a close sliding fit over a lower end of an upper downspout section. The sleeve member is shaped to provide a narrow gap between the sleeve member and the upper end of the tubular conduit leading into the chamber surrounding the tubular conduit.