Complexation thermodynamics of UO22+ and a series of N,N,N’,N’-tetraalkyl diglycolamide (TRDGA) ligands having alkyl chains –CH3 to –C6H13 were investigated in an ionic liquid (IL). The complexation constant for UO22+/DGA complex increased linearly with increasing alkyl chain length of DGA from tetramethyl (logβ1 = 4.52, logβ2 = 8.01) to tetrahexyl (logβ1 = 5.62, logβ2 = 10.3). There were two types of species recorded in the calorimetric titration for all the four ligands, one having endothermic complexation, and other exothermic. This observation was in contrast with those observed for aqueous medium, where both the stepwise complexation enthalpies were endothermic. The structural feature indicated the formation of [UO2L2]2+ type of complex without water or Tf2N− anion in the primary coordination sphere of the uranyl cation.