Plastic optical fibers (POFs) have been used to develop innovative plasmonic biosensors exploiting their characteristics, such as numerical aperture and multimode of the fiber, via extrinsic and intrinsic schemes. This work presents a simple approach to building innovative extrinsic POF sensor configurations, in which the complex processes required to achieve the sensing region in intrinsic POF-based sensors can be overcome by using 3D-printed supports combined with UV-cured optical adhesives. In this way, the shape of the optical waveguide can be changed simply by 3D printing, and the performance of the sensor can be tailored to the applications of interest by choosing the appropriate optical characteristics of adhesives and metal nanofilms. This kind of plasmonic probe can be combined with different types of molecular recognition elements, such as bio/chemical receptor layers, to achieve disposable biosensor chips with ultra-high binding sensitivity.