<p>This work introduces a tandem energy harvesting system (TEHS) using dual Savonius rotors with arc-shaped deflectors, which simultaneously act as vortex generators and rotational energy harvesters-a paradigm shift from static bluff bodies. The proposed rotor units effectively generate shedding vortices during rotation, and the fluctuating flow-induced loads are applied to a cantilever beam positioned downstream, the strain energy resulting from the oscillation of the beam can be effectively converted into electric energy. The power output from the cantilever beam increased when the proposed rotors were used as bluff bodies compared with cylinder bluff bodies, especially at lower inflow velocities. Under favorable conditions, the proposed TEHS achieved up to a 444.67% increase in performance compared to a traditional cylinder bluff body-equipped energy harvester. The study also revealed that 4-blade and 5-blade rotors significantly enhance energy harvesting when paired with extended deflectors. The rotor’s influence on the cantilever beam’s energy-harvesting performance and vibration characteristics were thoroughly investigated. Both the experimental results and the numerical modeling of fluid–structure interaction are used to evaluate the effectiveness of the energy harvesting system, and the work will provide new insights into the design and optimization of the flow induced vibration based energy harvesting system.</p>