Abstract The solid–liquid equilibria of five systems consisting of different pairs of pyrrolidinium-based ionic liquids were investigated. For all five tested systems the solid–liquid phase behaviour was found to be of eutectic type, and the eutectic compositions and temperatures were determined. Additional experiments were carried out to determine thermal stability of the resulting mixtures in comparison to the corresponding parent salts. Compared to the latter, melting point depression of the eutectic mixtures as large as 151 K are achievable for the system [C2MPyrr][NTf2] + [C4MPyrr][BF4]. At the same time, this is the first detailed analysis of eutectic mixture of ionic liquids involving four different ions that is reported in the literature.