Fluorescent nuclear track detectors (FNTDs) show excellent detection properties for heavy charged particles and have, therefore, been investigated in this study in terms of their potential for in-vivo range measurements. We irradiated FNTDs with protons as well as with C, Mg, S, Fe and Xe ion beams (3–9 MeV/u) over a broad range of fluences (4.5e5–1.0e11 cm−2) with the detectors' optical c-axis positioned perpendicular to the beam direction. All measured ion ranges (for single track as well as track bulk intensity irradiations) deviate less than 3% from tabulated SRIM data (Ziegler et al., 2009), independent of particle type, energy, fluence and linear energy transfer. Proton irradiation of detectors placed inside a polymethyl methacrylate (PMMA) phantom at the Heidelberg Ion-Beam Therapy Center showed promising results for future in-vivo FNTD applications.