The thermal properties of chelates of croconic acid and squaric acid with divalent copper, cobalt, nickel and zinc have been investigated by TG and DTA. The decreasing order of thermal stability for the decomposition of the croconate chelates was Ni > > Zn > Co=Cu and for the squarate complexes, Zn > Co=Cu > Ni. The copper croconate TG showed water loss in two distinct steps. This was rationalized on the basis of the already known Jahn-Teller effect for this molecule. The nickel squarate was thought to have a different structure than the other squarate chelates. Activation energies were calculated for the croconate chelates from their DTA curves.