The temperature dependence of the formation of negative ions from chlorinated phenols was studied. For all compounds, Cl − was produced and the intensity of the chloride ion increased with the increasing number of Cl atoms present in the molecule. For some of them, (M−HCl) −, (M−H) −, and M − (M: parent molecule) were also observed. The intensities of the fragment ions such as Cl − and (M−HCl) −, increased with the increasing temperature, though that of the parent anion decreased. There may be two mechanisms to produce (M−HCl) −. One is the HCl elimination of the hydroxylic hydrogen atom and the ortho-Cl atom. The other is the HCl elimination followed by the migration of the hydroxylic hydrogen atom to the ortho position for the 3,4- and 3,5-dichlorophenols. The branching ratio of [(M−HCl) −]/[Cl −] depends on the length of the HCl bond of the intermediate for the former mechanism.