In this study, we propose a novel dielectric modulated dual-dielectric bottom-gate top-contact organic thin film transistor (DMDDBG-OTFT) as a label-free biosensor for detecting neutral and charged bio-analytes. The device utilizes PVP and Al2O3 as dual-dielectric layers, offering superior sensitivity, selectivity, low leakage current, and low operating voltage compared to single-layer dielectrics. A sensing cavity is formed by etching the oxide under the drain region and biomolecule detection is based on changes in the drain current due to dielectric modulation from variations in dielectric constants and charge densities. Electrical parameters, including ION/IOFF, subthreshold slope (SS), and threshold voltage (VTH), were computed using a 2D Silvaco Atlas simulator. The DMDDBG-OTFT showed over 78% higher drain current sensitivity than conventional OTFT biosensors, with sensitivity reaching 5.59 × 1011 for charged gelatin biomolecules (K =12), a low limit of detection (LoD) of 13% and high selectivity. Additionally, temperature analysis from 265-315 K confirmed thermal stability, making the device promising for flexible biosensing applications.