Infrared neurostimulation has emerged in recent years as a promising technique for controlling neuronal activity without genetic manipulation. Having high absorption of the employed wavelengths as its fundamental mechanism, it requires implantable platforms to deliver light in brain regions deeper than the first cortical layers. Due to the spatial confinement of the stimulation, electrodes integrated in close proximity to the illumination spot are desirable to verify the effects of the stimulation by extracellular electrophysiology. Here we developed and validated in vivo a multifunctional neural interface based on a soft, biocompatible polymer optical fiber that allows simultaneous infrared neurostimulation and electrophysiology.