It is a pale yellow salt that rapidly absorbs water to form a hexahydrate, SmCl3.6H2O.

SmCl3 is prepared by the "ammonium chloride" route, which involves the initial synthesis of (NH4)2[SmCl5].

This material can be prepared from the common starting materials at reaction temperatures of 230 °C from samarium oxide:[2] The pentachloride is then heated to 350-400 °C resulting in evolution of ammonium chloride and leaving a residue of the anhydrous trichloride: It can also be prepared from samarium metal and hydrochloric acid.

Samarium(III) chloride is a moderately strong Lewis acid, which ranks as "hard" according to the HSAB concept.

The anhydrous chloride is used to prepare organometallic compounds of samarium, such as bis(pentamethylcyclopentadienyl)alkylsamarium(III) complexes.