The effect of copper toxicity on the photosynthetic activities and bioaccumulation in different tissues of Prosopis juliflora was investigated using three CuSO 4 concentrations (10, 50 and 100 mM) added under hydroponic conditions. Copper concentration and chlorophyll fluorescence were measured after 48 h of copper stress. The results obtained in this study show that increasing levels of 50 and 100 mM Cu 2+ resulted in a significant accumulation of this metal mainly in roots compared with control roots. On the other hand, our result showed a significant reduction of maximum photochemical efficiency of photosystem II (Fv/Fm) and the activity of photosystem II (F v /F 0 ) ratios in P. juliflora leaf treated with 100 mM Cu 2+ with respect to control after 4h of exposure. These changes suggested that the photosynthetic apparatus of P. juliflora was the primary target of the Cu 2+ action. Therefore the information provided by this short-term (48 h) experiment in P. juliflora showed that several physiological processes are activated, in which the copper uptake by roots and their accumulation in tissues play a central role. In conclusion, the chlorophyll fluorescence parameters can be used as a useful physiological tool to assess early changes in photosynthetic performance of P. juliflora in response to copper pollution in short-term. Finally, the present study showed that P. juliflora is a promising prospect for heavy metals phytoremediation purposes occurring in arid and semi-arid climates in the northwest Mexico.