Resumo. Costalimaita ferruginea (Fabricius) (Coleoptera: Chrysomelidae) is the main Coleoptera defoliator of eucalyptus in Brazil and has a strong association with plants of the family Myrtaceae, bein the eucalyptus important for the sectors of energy, paper, pulp and furniture industry. The objective of the present study was to record the occurrence of this Chrysomelidae in eucalyptus plants in Sinop, State of Mato Grosso, Brazil, during the months of November 2010 to January 2011, thus contributing to increase in knowledge on the geographic distribution of this insect and also hypothesize that the Coleoptera may soon become a major pest of eucalyptus in the state of Mato Grosso.