We propose a novel joint calibrationless reconstruction for accelerating multi-shot navigator-free DTI, using a low-rank completion approach. The redundant information across different directions is utilized to facilitate the reconstruction, including sharable coil sensitivities and anatomical structures. A 3D Hankel tensor was constructed and its concatenated Hankel matrices were used for low-rank approximation. In vivo human brain DTI experiment shows that the proposed joint reconstruction can reduce artifacts in diffusion-weighted images, and yield more accurate DTI metrics, when compared with separate reconstruction for different directions. This method also presents a new potential reconstruction strategy for fast high-resolution DTI.