Two inorganic–organic hybrid compounds, (H₂dabco-CH₂-Cl)[M^IICl₄] (M = Co, Zn; H₂dabco-CH₂-Cl = 1-chloromethyl-1,4-diazabicyclo[2.2.2]octan-1,4-diium cation), were synthesized under slow evaporation conditions. DSC measurements indicated that compounds (H₂dabco-CH₂-Cl)[M^IICl₄] (M = Co, Zn) underwent reversible phase transitions at 355 K and 358 K with hysteresis widths of 4 K and 5 K, respectively. Temperature-dependent dielectric measurements also confirmed the phase transitions. Variable-temperature X-ray diffraction data demonstrated that the phase transition was from a high-temperature phase with the space group Pnma to a low-temperature phase with the space group P2₁/c. The disorder–order transformation of the terminal Cl atom of the (H₂dabco-CH₂-Cl)²⁺ cation triggered by the decrease in temperature may drive the phase transition.