The weakly coordinating anion [Me3NB12Cl11]− has been prepared by a simple two‐step procedure. The anion [Me3NB12Cl11]− is easily obtained in batches of up to 20 g by chlorination of the known [H3NB12H11]− anion with SbCl5 at about 190 °C and subsequent N‐methylation with methyl iodide. Starting from Na[Me3NB12Cl11], several synthetically useful salts with reactive cations ([NO]+, [Ph3C]+, and [(Et3Si)2H]+) were prepared. Full spectroscopic (NMR, IR, Raman, TGA, MS) characterization and single‐crystal X‐ray diffraction studies confirmed the identity and purity of the products. The thermal, chemical, and electrochemical stability as well as the basicity of the [Me3NB12Cl11]− anion is similar to that of the structurally related weakly coordinating 1‐carba‐closo‐dodecaborate and closo‐dodecaborate anions. The facile preparation of the [Me3NB12Cl11]− anion and its ideal chemical and physical properties make it a cheap alternative to other classes of weakly coordinating anions.