This work introduces a novel approach for enhancing the detection capability of localized surface plasmon resonance (LSPR) optical fiber sensors through the application of a zeroth-order Bessel-Gauss beam in a tapered multimode fiber setup. Traditional LSPR sensors using Gaussian beams in linear fiber geometries often face limitations in achieving strong light-matter coupling. To address this, the Bessel-Gauss beam’s non-diffracting nature and extended depth of focus are leveraged to improve plasmonic excitation on metallic nanoparticle layers. Various structural parameters, including the fiber core dimension, taper geometry, and ambient refractive index (RI) are systematically explored. Simulation outcomes indicate that decreasing the core size and increasing the tapering ratio improve confinement of the evanescent field, resulting in heightened RI sensitivity. Furthermore, the observed spectral shifts with changing environmental RI confirm the sensor’s responsiveness. These findings underscore the benefits of integrating beam shaping techniques with tapered fiber designs to develop highly sensitive LSPR sensors suitable for environmental sensing, medical diagnostics, and biochemical applications.