The invention provides a heat exchanger fin, a heat exchanger, an indoor unit and an air conditioner. The heat exchanger fin comprises a fin body, the fin body comprises an air outlet contour line onone side and an air inlet contour line on the other side, and the fin body is provided with a plurality of refrigerant pipe mounting holes. On the straight line where the curvature radius of the air outlet contour line of the fin body is located or on the straight line where the curvature radius of the air inlet contour line of the fin body is located, the distance between the air inlet contour line and the air outlet contour line of the fin body is gradually reduced from the middle of the heat exchanger fin to the two ends. The inner diameters of the refrigerant pipe mounting holes are gradually reduced from the middle part of the heat exchanger fin to the two ends. According to the technical scheme, the utilization rate of the heat exchanger fin can be improved, the heat exchange efficiency is improved, the energy consumption is reduced, material waste can be reduced, and the production cost is reduced.