The composite approach is very effective in developing multiferroic systems with remarkable magnetoelectric coupling coefficients. In this work, P(VDF-HFP)-based films containing 2, 4, 8 and 16 wt% Y3Fe5O12–Na0.5K0.5NbO3 nanocrystalline particles were developed via a simple solvent cast process. In order to facilitate the β-phase crystallization of the P(VDF-HFP), hydrated ferric nitrate was utilized during the preparation of the films, which resulted in significant improvement in the β-phase content. Moreover, the use of Y3Fe5O12–Na0.5K0.5NbO3 also triggered the β-phase crystallization of the P(VDF-HFP). At the highest filler loading of 16 wt%, a magnetoelectric coefficient of 33.6 mV cm−1 Oe−1 was achieved. Piezoelectric energy harvesting studies were also carried out using the composite film containing 16 wt% Y3Fe5O12–Na0.5K0.5NbO3 nanocrystalline particles. A maximum open-circuit voltage of 3.79 V was measured when a compressive force of 5 N was applied to the energy harvesting device.