Single-crystal ${\mathrm{K}}_2\mathrm{Zn}{\mathrm{Cl}}_4$ doped with ${\mathrm{Co}}^{2+}$ has been grown successfully by use of the Czochralski technique. The absorption spectrum of the crystal was measured. The most intense line, centered at $650\mathrm{nm}$ , was associated with the transition ${}^{4}A_2\to {}^{4}T_{1P}$ , and a novel and important result that corporate transition (co-transition) between ${}^{4}A_2\to {}^{4}T_{1F}$ and ${}^{4}A_2\to {}^{4}T_2$ of ${\mathrm{Co}}^{2+}$ in the region of $1300–2400\mathrm{nm}$ was found and discussed. The mechanism that caused the phenomenon was explained by energy-level splitting theory. In the tetrahedral approximation, using the quantum and Tanaba–Sugano theories, Racah parameter B and crystal field parameter 10Dq were calculated. The optical energy gap, deduced to be $4.82\mathrm{eV}$ , was lower than that of pure ${\mathrm{K}}_2\mathrm{Zn}{\mathrm{Cl}}_4$ .