Carbamazepine (CBZ) is one of most frequently detected pharmaceutical contaminants in water ecosystem, which cannot be removed efficiently by traditional techniques. Degradation of CBZ by peroxymonosulfate (PMS) activated with organo-montmorillonite supported nCoFe(2)O(4) (nCoFe(2)O(4)/OMt) was investigated in this study. The degradation efficiency of CBZ (5 mg L-1) was 93% within 60 min in the presence of 0.4 g L-1 nCoFe(2)O(4)/OMt and 0.5 mM PMS at pH 6.8 and 25 degrees C, following a pseudo-first order kinetics. High PMS concentration and low initial pH could enhance CBZ degradation. The presence of Cl-, NO3- and HCO3- showed marked enhancement, slight suppression and obvious inhibition of CBZ degradation, respectively. High concentration of humic acid could decrease the CBZ degradation. X-ray photoelectron spectroscopy of nCoFe(2)O(4)/OMt before and after reaction revealed that both Co2+/Co3+ and Fe2+/Fe3+ were involved in PMS activation during the CBZ degradation. Electron paramagnetic resonance and radical scavenger experiments confirmed that both center dot OH and SO4 center dot- played a predominant role on the CBZ degradation. The degradation products were identified by LC-MS/ MS to understand the possible pathways.