Three novel potassium-zinc borohydrides/chlorides are described. KZn(BH₄)₃ and K₂Zn(BH₄)_<i>x</i>Cl_4-<i>x</i> form in ball-milled KBH₄:ZnCl₂ mixtures with molar ratios ranging from 1.5:1 up to 3:1. On the other hand, K₃Zn(BH₄)_<i>x</i>Cl_5-<i>x</i> forms only in the 2:1 mixture after longer milling times. The new compounds have been studied by a combination of in situ synchrotron powder diffraction, thermal analysis, Raman spectroscopy, and the solid state DFT calculations. Rhombohedral KZn(BH₄)₃ contains an anionic complex [Zn(BH₄)₃]⁻ with <i>D</i>₃ (32) symmetry, located inside a rhombohedron K₈. KZn(BH₄)₃ contains 8.1 wt % of hydrogen and decomposes at 385 K with a release of hydrogen and diborane similar to other Zn-based bimetallic borohydrides like MZn₂(BH₄)₅ (M = Li, Na) and NaZn(BH₄)₃. The decomposition temperature is much lower than for KBH₄. Monoclinic K₂Zn(BH₄)_<i>x</i>Cl_4-<i>x</i> contains a tetrahedral complex anion [Zn(BH₄)_<i>x</i>Cl_4-<i>x</i>]²^- located inside an Edshammar polyhedron (pentacapped trigonal prism) K₁₁. The compound is a monoclinically distorted variant of the paraelectric orthorhombic <i>ht</i>-phase of K₂ZnCl₄ (structure type K₂SO₄). K₂Zn(BH₄)_<i>x</i>Cl_4-<i>x</i> releases BH₄ starting from 395 K, forming Zn and KBH₄. As the reaction proceeds and <i>x</i> decreases, the monoclinic distortion of K₂Zn(BH₄)_<i>x</i>Cl_4-<i>x</i> diminishes and the structure transforms at 445 K into the orthorhombic <i>ht</i>-phase of K₂ZnCl₄. Tetragonal K₃Zn(BH₄)_<i>x</i>Cl_5-<i>x</i> is a substitutional and deformation variant of the tetragonal (<i>I</i>4/<i>mcm</i>) Cs₃CoCl₅ structure type possibly with the space group <i>P</i>4₂/<i>ncm</i>. K₃Zn(BH₄)_<i>x</i>Cl_5-<i>x</i> decomposes nearly at the same temperature as KZn(BH₄)₃, i.e., at 400 K, with the formation of K₂Zn(BH₄)_<i>x</i>Cl_4-<i>x</i> and KBH₄, indicating that the compound is an adduct of the two latter compounds.Read less <