In the title compound, CH(3)NH(3) (+)·BF(4) (-)·C(12)H(24)O(6), the methyl-ammonium cation makes three N-H⋯O hydrogen bonds to the 18-crown-6 mol-ecule. The -NH(3) (+) and -CH(3) groups of the cation adopt a staggered conformation. The F atoms of the tetra-fluoridoborate anion are disordered over two sets of sites in a 0.519 (11):0.481 (11) ratio. Weak C-H⋯F inter-actions occur in the crystal, which possibly correlate with the anion disorder.