This study presents the implementation of an evanescent field (EF)-based sensing platform employing a hybrid film composed of graphene oxide (GO) and poly(methyl methacrylate) (PMMA), integrated onto coreless D-shaped fibers (cDsFs). The operational framework of the hybrid film-coated cDsFs (GoP-cDsFs) was comprehensively elucidated through theoretical and experimental analyses. To establish a baseline for comparison, the performance of the cDsFs with the sole inclusion of the PMMA film was investigated. Our investigations underscore the substantive role of graphene oxide in augmenting the evanescent field, thereby generating a synergistic effect that contributes to the overall enhancement of the evanescent field in the device. Consequently, the fabricated GoP-cDsF sensor manifests an outstanding sensitivity of -4.936 nm/°C, rendering it particularly well-suited for applications demanding high-sensitivity temperature sensing. Moreover, the unique attributes of the GoP-cDsF position it as a promising candidate for the measurement of both magnetic and electric fields, presenting an effective strategy for multifunctional sensing applications.