This paper presents an estimation of power output produced by an Electro-Active Paper (EAPap) energy harvesting transducer under base vibration. EAPap is very thin cellulose piezoelectric film, which exhibits a direct piezoelectric effect, when subjected to stress. A 50x50 mm(2) EAPap patch was bonded on a 100x50x1 mm(3) aluminum cantilever structure. Energy harvesting tests were performed on the energy harvesting transducer, without and with a 2 grams proof mass near the tip of the cantilever beam. The voltage, current and power frequency response functions (FRFs) with respect to the base acceleration are identified and presented. The Voltage FRFs show a monotonic trend with increasing the load resistor from 100 k Omega to 1 M Omega, and the current FRFs also demonstrate monotonic dynamic behavior, but the trend is opposite to the voltage FRFs. In contrast to the voltage and current FRFs, the output power FRFs do not show a monotonic trend, exhibiting the maximum value of 150 mu W/g(2) at 75.1 Hz without the proof mass. The output power increases to 392 mu W/g(2) at 62.2 Hz when the proof mass is attached. This preliminary study indicates that EAPap is promising for energy harvesting transducers under vibration environment.