Abstract. Abstract Aim Contributing to taxonomic knowledge on Pigmented Euglenophyceae at the Upper Paraná River Floodplain by enlarging the biodiversity survey in this ecosystem, in addition to contributing to the knowledge on the geographical distribution of this group in Brazil. Methods Quarterly samplings in the limnetic region of a floodplain lake between February 2000 and March 2009, numbering 30 samples obtained from both vertical and horizontal trawls using plankton net of a 15 µm-mesh aperture and subjected to Transeau-solution preservation. We prepared temporary slides and analyzed in order to have the organisms identified, measured and photographed through digital camera, directly using an Olympus binocular optical microscope with a 400x/1000x magnification. The analysis included the calculation of Constancy (C) for the sample of each species. Results 36 taxa were identified. Genus Trachelomonas Ehr. emend. Defl. had the best representation, with 20 taxa. Among the taxa surveyed, 53% (19 taxa) constituted new records of occurrence for the Upper Paraná River Floodplain. The taxa recorded as frequent (33.3%) are considered cosmopolitan and present wide geographical distribution throughout Brazil; however, most of the taxa surveyed (67%) was classified as sporadic or rare, which is probably related to the high environmental variability observed along the study period. Conclusion Among the surveyed 19 taxa constituted new records of occurrence for the upper Paraná River floodplain and extended the geographical distribution of Euglenophyceae in Brazil.