The rapid expansion in the study and use of ionic liquids (ILs) is a result of their unique properties including negligible volatility, high thermal stability, and ability to dissolve disparate compounds. However, because ILs have infinitely variable structures (often referred to as "tunability"), these properties can differ considerably. Herein, we focus on the thermal stability of 15 bis-/dicationic ionic liquids. Specifically, their thermal breakdown products are examined to determine the structural linkages, bonds, or atoms most susceptible to thermally induced changes and whether such changes occur before possible volatilization. In most cases, the heteroatom-carbon single bonds were susceptible to thermolytic decomposition. Graphical abstract Capture of dicationic ionic liquid thermal decomposition products for subsequent identification.