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Summary: The cut‐in wind speed and the power output are the two main concerns of a galloping energy harvester. A good galloping energy harvester is expected to have a low cut‐in wind speed and a high power output. This paper proposes a two‐degree‐of‐freedom (2‐DOF) galloping‐based piezoelectric energy harvester (GPEH) by mounting a secondary beam onto a primary piezoelectric cantilever beam. An experimental study is conducted to evaluate the actual energy harvesting performance of the proposed 2‐DOF GPEH. The effects of the secondary beam length and the mounting position on the cut‐in wind speed and the power output are investigated. It is revealed that the introduction of the secondary beam can reduce the cut‐in wind speed from 2.372 m/s to 1.961 m/s. Mounting the secondary beam further away from the bluff body weakens the influence of the secondary beam on the energy harvesting performance of the 2‐DOF GPEH. Moreover, the power output can be increased or decreased by tuning the secondary beam length. The power output from a well‐tuned 2‐DOF GPEH can be increased for about 111.1%, as compared to the conventional 1‐DOF GPEH. By contrast, the power output from a badly tuned 2‐DOF GPEH is reduced for about 22.2%. A simple theoretical model is developed for explaining the experimentally observed phenomenon and can be used to provide some guidelines in the design of 2‐DOF GPEH to avoid performance deterioration. [ABSTRACT FROM AUTHOR]