Short-term experiments were carried out to study the feeding performances of the copepod Euterpina acutifrons fed on Thalassiosira weissiogii. Four adult females of this species were sorted and transferred to 15 ml glass bottles filled with different dilutions of the diatom cultures to obtain cell concentrations of 7.5, 10.0, 12.5, 15.0, 17.5, 20.0, 22.5 and 25.0 x 103 cell.ml-1 (8 treatments, 3 replicates, 4 copepods/replicate). Initial and final cell concentrations of control and experimental bottles were determined using a Neubauer Chamber. Filtration and ingestion rates were measured thought 1 hour grazing trials performed under controlled laboratory conditions. Filtration rates of Euterpina acutifrons oscillated from 0.81 to 2.92 ml. copepod-1 .h-1 and they significantly higher (p<0.05) on 7.5 x 103 cell.ml-1 concentration. Ingestion rates varied between 1.8 and 8.13 x 103 cell.copepod-1.h-1, showing significative differences (p<0.05) between treatments with low (7.5 x 103 cell.ml-1) and high (22.0 x 103 cell.ml-1) number of cells. The feeding rates of Euterpina acutifrons fed on Thalassiosira weissüogii revealed the important hole of this species of copepod on the aquatic food web of coastal ecosystems of the Amazonian region, especially on the northeast of Pará where it is commonly found.