As a polyamine, triethylenetetramine (TETA) has not only a lower vapour pressure than diethylenetriamine (DETA) but it is also a more powerful chelating agent for the control of metal ions that can be the cause of an inadvertent activation and catalytic oxidation in flotation. The effect of this reagent on the depression of a hexagonal pyrrhotite (non-magnetic) was investigated on a bench scale using a massive nickel-copper sulphide ore sample. Mineral composition of the ore was estimated from mass balance equations of relevant elements. This allowed examination of the flotation selectivity between minerals, primarily between pentlandite and pyrrhotite. The pentlandite-pyrrhotite flotation selectivity obtained with TETA and sodium metabisulfite (SMBS), respectively, was similar to that obtained under baseline conditions. However, the combined use of TETA and SMBS produced an excellent separation of the two minerals resulting in a much greater concentrate grade. Possible mechanisms on the action of reagents are discussed.