There is increasing interest in the use of autotrophic microalgae as alternative sources of eicosapentaenoic acid (EPA), a nutritionally important polyunsaturated fatty acid that plays a key role in the prevention and treatment of several human diseases and disorders, for incorporation in either aquaculture feeds or human diets. In this study, we have demonstrated the feasibility of outdoor cultivation of the prymnesiophyte, Pavlova viridis, one of the most promising photoautotrophic producers of EPA, in tubular photobioreactors (PBR). P. viridis was cultivated in photobioreactors of two sizes (six-tube and eight-tube) in autumn under the climatic conditions of Nanjing, China. In both photobioreactors the microalgal cells quickly adapted to the new environments outdoors when cultivated with agitation, and had a very short lag growth phase. Chlorophyll a contents ranged from 0.037 to 0.066 g 106 cells-1 and from 0.041 to 0.063 g 106 cells-1 for the 6-tube and 8-tube PBR, respectively. Decreasing temperature and light intensity increased the proportion of polyunsaturated fatty acids in cultures of P. viridis to 29.9 and 35.9 in the six- and eight-tube PBR, respectively. Cultivation of P. viridis in our closed tubular photobioreactor represents a suitable approach for the production of a high-quality microalgal biomass enriched in EPA.