The solvent extraction of yttrium and rare earth elements from copper pregnant leach solutions (PLS) using Primene JM-T, a primary aliphatic amine, has been studied. This investigation focused on the effect of extractant concentration to obtain a better understanding of the extraction mechanism. Copper bearing PLS from a leaching operation in Arizona was used as the feed solution in all experiments. Standard experimental conditions were 5 min contact time, 1:1 O:A phase ratio, kerosene as a diluent, and room temperature. The solution chemistry of the PLS was modeled using PHREEQC software. Primene JM-T concentrations in the organic phase ranged from 0.059-0.221 M (2-7.5% v/v). At 0.147 M Primene JM-T, yttrium extraction was 88.4% whereas the LREEs averaged about 95% and the HREEs a little lower at 92%. It was shown that approximately 2.4 mol of Primene JM-T are required per mole of yttrium or rare earth metal at extractant concentrations ranging from 0.07 to 0.10 M. In this Primene JM-T concentration range, it appears that a mixture of metal sulfate complexes is being extracted. At low Primene JM-T concentrations, Me(SO4)(3)(3-) is the dominant species being extracted. As extractant concentrations increases, the reaction appears to favor of the extraction of Me(SO4)(2)(-).