A magnetically recyclable and highly photocatalytic NiFe2O4/multi-walled carbon nanotubes (NiFe2O4/MWNT) photocatalyst with differing MWNT content has been successfully prepared via a one-step hydrothermal method. In this study, NiFe2O4 is not only used as the magnetic material but also acts as the photocatalyst. It is interesting that in the presence of MWNT the poorly active nanocrystals of NiFe2O4 are dramatically converted into a highly active catalyst. The highly photocatalytic activities are evaluated by the degradation of phenol, o-nitrophenol (ONP), p-nitrophenol (PNP), and picric acid (PA) under ultraviolet light irradiation. The significant enhancement in photoactivity can be attributed to the synergistic effect between NiFe2O4 and MWNT: the effective charge transfer from NiFe2O4 to MWNT and thus the suppressed recombination of electron-hole pairs of the composite. Moreover, the remarkable magnetic properties of NiFe2O4/MWNT give a more convenient way to recycle the photocatalysts. (c) 2012 Elsevier B.V. All rights reserved.