Cs₂SnX₆ (X = Cl, Br, and I) compounds have emerged as promising lead-free and ambient-stable materials for photovoltaic and optoelectronic applications. To advance these promising materials, it is crucial to determine the correlations between physical properties and their local structure and dynamics. Solid-state NMR spectroscopy of multiple NMR-active nuclei (¹³³Cs, ¹¹⁹Sn, and ³⁵Cl) in these cesium tin(IV) halides has been used to reveal the atomic structure, which plays a key role in the materials’ optical properties. The ¹¹⁹Sn NMR chemical shifts span approximately 4000 ppm, and the ¹¹⁹Sn spin-lattice relaxation times span 3 orders of magnitude when the halogen goes from chlorine to iodine in these diamagnetic compounds. Moreover, ultrawideline ³⁵Cl NMR spectroscopy of Cs₂SnCl₆ indicates an axially symmetric chlorine electric field gradient tensor with a large quadrupolar coupling constant of ca. 32 MHz, suggesting the presence of a chlorine moiety that is directly attached to Sn(IV) ions. Variable-temperature ¹¹⁹Sn spin-lattice relaxation time measurements support the presence of dynamics of octahedral SnI₆ units in Cs₂SnI₆. We further show that complete mixed-halide solid solutions of Cs₂SnCl_xBr_6–x and Cs₂SnBr_xI_6–x (0 ≤ x ≤ 6) form at any halogen compositional ratio. ¹¹⁹Sn and ¹³³Cs NMR spectroscopy resolve the unique local SnCl_nBr_6–n and SnBr_nI_6–n (n = 0–6) octahedral and CsBr_mI_12–m (m = 0–12) cuboctahedral environments in the mixed-halide samples. The experimentally observed ¹¹⁹Sn NMR results are consistent with magnetic shielding parameters obtained by density functional theory computations that were obtained to model the random halogen distribution in mixed-halide analogues. Finally, we demonstrate the difference in the local structures and the optical absorption properties of Cs₂SnI₆ samples prepared by solvent-assisted and solvent-free synthesis routes.