The olive mill wastewater (OMW), arises during the production process of olive oil, is an important problem in all Mediterranean countries. OMW shows seasonality, and contain high organic pollutant. Eventhough various methods have been studied for the treatment, olive oil producers neither can afford the cost of these methods, nor it can provide the discharge standards. The capacity of phytoremediation of Vetiveria zizanioides (L.) Nash (vetiver) and Cyperus alternifolius L. (umbrella palm) species was evaulated in the treatment of OMW by floating treatment wetland (FTW) method. The 5 and 15% concentrations of OMW (OMW-5 and OMW-15) were remediated by these plants, and unplanted sets as triplicates for 67 days to determine their organic and nitrogen reduction. Therefore, total organic carbon (TOC), total phenol and total nitrogen (TN) in the OMW were measured. The amount of biomass at the beginning of the experiment were 2.5 and 4.0 kg OMW-5 and OMW-15 respectively. The highest biomass growth rate (149%) and total phenol accumulation in plant (439%) were observed in umbrella palm. The results showed that umbrella palm achieved 95%, 99%, 82% removal in TOC, total phenol, TN while these removals were 85%, 93%, 40% in vetiver planted OMW-5 tanks. Similarly, the removal in OMW-15 were comparable with 90, 97, 41 percentages with umbrella palm and 79, 92, and 21 percentages for vetiver respectively. As a result, it seems that umbrella palm and vetiver have potential in diluted OMW treatment by FTW for future.