Uranyl complexes of the type [UO 2(TBAD)(NO 3) 2], where TBAD is N, N, N′, N′-tetra- n-butyl aliphatic diamide, Bu 2NCO(CH 2) n CONBu 2, with n being 1, 2, 3, 4, 6, 8 or 10, were all prepared (TBAD with n = 0 failed to form a complex of this type) and characterized by elemental analysis, and UV-vis and IR spectroscopy. The complexes were found to have a chelate structure with three bidentate ligands, one TBAD molecule and two NO − 3 groups, all coordinated through O atoms. Using single-crystal XRD, the complex with n = 2 in TBAD was revealed to have a deformed hexagonal bipyramid structure with a large organic ligand chelate ring. The thermal decomposition studies of the complexes were carried out in nitrogen atmosphere using TG-DTG techniques. The kinetic parameters (non-isothermal method) for the main TBAD decomposition step were evaluated using the method suggested by Málek, Šesták, Koga et al. Based on the above characterizations the effects of carbon chain length in TBAD on the structure, stability, and thermal behaviour of the complexes, were carefully observed and discussed. The results showed that not only the E value, but also the TBAD decomposition pattern and mechanism for the complex with n = 1 in TBAD are distinct from those of all the others.