The high-level ab initio potential energy surface (PES) for NeCl₂ in the ground electronic state predicts the energy minimum in the linear geometry (L-well) to be slightly deeper than that in the T-shaped geometry (T-well). The experimental D₀ and R₀ values are reproduced within uncertainties of measurements by both adding the calculated perturbation of the Ne-Cl interactions due to intramolecular forces in Cl₂ to empirical NeCl potentials, and by linearly extrapolating or simply scaling the ab initio PES. These procedures lead to equal or even reversed relative depths of the two wells, in accord with both predictions of an atom-atom model using equivalently accurate ab initio NeCl potentials and variation of the ab initio PES with increasing accuracy of calculations. The D₀ value for the L-well is predicted to be less than that for the T-well by 2.4 to 5.2 cm^-1 for different scaling schemes. The calculated lowest energy rovibrational states associated with each of two conformers show negligible mutual influence, while the effect of the L-well on the rovibrational wave functions for the next vibrational states associated with the T-well is found to be rather important. Microwave spectra are predicted for each PES obtained, and include portions originating from the L-well. The calculated scattering cross section reproduces well the experimental data and is found to be significantly contributed by the L-well.