In the title salt, C(12)H(20)NO(+)·CH(3)SO(3) (-), the [1-(1-adamantyl-amino)ethyl-idene]oxonium cations and methane-sulfonate anions are linked into chains along the a axis via O-H⋯O and N-H⋯O hydrogen bonds. All non-H atoms of the acetamido group are essentially planar, with a maximum deviation of 0.0085 (12) Å. In comparison with related structures, the carbonyl C=O bond is slightly elongated [1.249 (2) Å], whereas the amide C-N bond is shortened [1.292 (2) Å].