Present work focuses on the differences in the performances obtained in the froth flotation of copper smelter slag with multiple collector viz, sodium iso-propyl xanthate (SIPX), sodium di-ethyl dithiophosphate (DTP) and alkyl hydroxamate at various dosages. Flotation tests were carried out using single collectors as well as various mixtures of the two collectors at different but constant total molar concentrations. Flotation performances were increased effectively by the combination of collectors. The findings show that a higher copper recovery (84.82%) was obtained when using a 40:160 g/t mixture of sodium iso-propyl xanthate (SIPX) with di-ethyl dithiophosphate compared to 78.11% with the best single collector. Similar recovery improvement (83.07%) was also observed by using a 160:40 g/t mixture of sodium iso-propyl xanthate (SIPX) with alkyl hydroxamate. The results indicate that in both cases DTP and alkyl hydroxamate played important role as co-collector with SIPX for the recovery of coarse interlocked copper bearing particles and has an important effect on the behaviour of the froth phase. However, comparatively higher mass recovery was obtained when hydroxamate was used as a co-collector, accompanied by poorer copper grades. In this context the co-collector DTP is advantageous for the improvement of copper grade and recovery from copper smelter slag. (C) 2015 Elsevier B.V. All rights reserved.