For the first time, the ³(X + M)LCT origin of both the lowest excited triplet states of dual-emissive tetranuclear copper(I)-iodide complexes with the octahedral Cu₄I₄ core has been revealed using quantum chemical computations in contrast to the conventional assignment of the lowest-energy emission to the ³CC state. The unusual thermochromic behavior shown for dual emission from these states of Cu₄I₄ clusters stabilized by P,N-ligands allows optical ratiometric thermal sensing in a broad temperature range.