Repulsive and long-range exciton-exciton interactions are crucial for the exploration of one-dimensional (1D) correlated quantum phases in the solid state. However, the experimental realization of nanoscale confinement of 1D dipolar exciton has thus far been limited. Here, we demonstrated atomically precise lateral heterojunctions based on transitional-metal dichalcogenides (TMDC) as a new platform for 1D dipolar excitons. The dynamics and transport of the interfacial charge transfer excitons in a type II WSe2-WSSe lateral heterostructure were spatially and temporally imaged using ultrafast microscopy. The expansion of the exciton cloud driven by dipolar repulsion was found to be strongly density dependent and highly anisotropic. The interaction strength between the 1D excitons was determined to be ~3.9 × 10^-14 eV cm^-2 corresponding to a dipolar length of 310 nm, which is a factor of 2-3 larger than the interlayer excitons at two-dimensional van der Waals vertical interfaces. These results suggest 1D dipolar excitons with large static in-plane dipole moment in lateral TMDC heterojunctions as a new system for investigating quantum many-body physics.