The main objective of the work was to investigate about the feasibility to produce high quality bio-oil from Mediterranean sea plant by catalytic pyrolysis process. Therefore, experiments using Posidonia Oceanica at 500 degrees C in a fixed bed reactor were explored taking into consideration the biomass conversion and bio-products yields. The effect of different "home-made" Ni, Ce, HZSM-5 based catalysts in pyrolysis process was analyzed mainly in terms of conversion yield, bio-oil yield and bio-oil oxygen and organic compounds content. The highest liquid yields were obtained at 500 degrees C. Particularly, CeO2 (51.15 wt%), NiCe/HZSM-5 (50.66 wt%) and Ni/CeO2 (49.74 wt%) were the most effective catalysts and these have increased the bio-oil yield compared to non -catalytic ones (47.74 wt%). The highest conversions were obtained with Ni/HZSM-5 (80.81%) and CeO2 (79.07%) which were the most efficient catalysts. Oxygen level was decreased in bio-oils from 25.66 wt% in the starting biomass to 6-8 wt% with CeO2, Ni/CeO2 and NiCe/HZSM-5 catalysts. This is due to the potential of these catalysts to promote deoxygenation reactions, such as dehydration, decarboxylation and decarbonylation, that enhance the bio-oil quality. In terms of compositions zeolite and ceria based catalysts were the best. In absolute the highest content of hydrocarbons was obtained with HZSM-5 and Ni/HZSM-5, 39.56 and 34.91% respectively. Therefore, lower content of acids and oxygen in the bio-oil, higher hydrocarbons, combined with higher heating value show promise for production of high-quality bio-oil from Posidonia Oceanica via catalytic pyrolysis. (C) 2017 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.