Due to its anticuprate Ti₂O layer and its fascinating phase diagram with a large coexistence area of superconductivity and a density wave phase, the new class of titanium based superconductors attracts great scientific interest. In this paper we report μSR investigation on powder samples of Ba_1-xNa_xTi₂Sb₂O (x = 0, 0.15, 0.25). Our results exhibit both the presence of a charge density wave and superconductivity in Ba_1-xNa_xTi₂Sb₂O. The superconducting order parameter, extracted from a vortex state analysis using the numeric Ginzburg-Landau model, is compatible with a s-wave symmetry. In the universal Uemura classification of superconductors this compound is at the verge of unconventional superconductivity.