Cobalt chloride can be prepared in aqueous solution from cobalt(II) hydroxide or cobalt(II) carbonate and hydrochloric acid:
: + 2 HCl →   +    +  
: + 2 HCl  →   +  2
The solid dihydrate and hexahydrate can be obtained by evaporation.  Cooling saturated aqueous solutions yields the dihydrate between 120.2 °C and 51.25 °C, and the hexahydrate below 51.25 °C. Water ice, rather than cobalt chloride, will crystallize from solutions with concentration below 29%. The monohydrate and the anhydrous forms can be obtained by cooling solutions only under high pressure, above 206 °C and 335 °C, respectively.
The anhydrous compound can be prepared by heating the hydrates.
On rapid heating or in a closed container, each of the 6-, 2-, and 1- hydrates partially melts into a mixture of the next lower hydrate and a saturated solution—at 51.25 °C, 206 °C, and 335 °C, respectively. On slow heating in an open container, so that the water vapor pressure over the solid is practically zero, water evaporates out of each of the solid 6-, 2-, and 1- hydrates, leaving the next lower hydrate, at about 40°C, 89°C, and 125°C, respectively.  If the partial pressure of the water vapor is in equilibrium with the solid, as in a confined but not pressurized contained, the decomposition occurs at about 115°C, 145°C, and 195°C, respectively.
Dehydration can also be effected with trimethylsilyl chloride:
:•6 + 12  →  + 6 + 12 HCl
The anhydrous compound can be purified by sublimation in vacuum.