The present work demonstrates a simple and efficient route to synthesize a variety of barium titanate (BaTiO3) nanostructures including nanowires, nanoswords, nanostars, nanocubes, and nanoparticles by a facile hydrothermal approach. The experiments showed that different morphologies can easily be tuned by varying the concentration of precursors, i.e., hydrogen titanate (H2Ti3O7) and barium hydroxide octahydrate (Ba(OH)2.8H2O), while keeping the molar ratio, reaction temperature and time fixed. The structure and morphology of BaTiO3 were characterized by field emission scanning electron microscopy (FESEM) and X-ray diffraction (XRD). The results indicate that BaTiO3 nanowires are in cubic phase with an average diameter of 80-100 nm. The shape of BaTiO3 changes from nanowires to nanoparticles with an increase in Ba(OH)2.8H2O concentration from 0.08 M to 0.51 M. Two possible mechanisms, in-situ topotactic transformation reaction and dissolution-deposition reaction have been suggested for different morphologies of BaTiO3.  The synthesized 0-D and 1-D BaTiO3 nanostructures are promising materials for many applications because of their excellent dielectric, ferroelectric and piezoelectric properties. The present work will open a new route to single reaction parameter dependent synthesis of 0- and 1-D BaTiO3 nanostructures which can find a range of applications including electronics, catalysis, energy harvesting, etc.