A heat exchanger, a heat exchanger unit, and a refrigeration cycle apparatus improve a heat exchange performance, a discharge performance, and a frosting resistance, and each include: a flat tube; a fin formed in the shape of a plate having a plate surface extending in a longitudinal direction of the fin that is perpendicular to a width direction thereof, coincides with an up/down direction, and crosses the tube axis of the flat tube; and a first water conveyance member provided below the fin. The first water conveyance member has: a first upper surface facing a lower end portion of the fin; a first ridge located at one end portion of the first upper surface; and a second ridge located at the other end portion of the first upper surface.