This article presents the results of the translation and cross-cultural adaptation of the Informant Questionnaire on Cognitive Decline in the Elderly (IQCODE) and the test-retest reliability of a version to be used in Brazil. An instrument review committee analyzed the conceptual and item equivalence. In order to analyze semantic equivalences, three translations and three back-translations were performed; a summary version was devised and pre-tested, and a test version elaborated. The Cronbach's +/- coefficient and intraclass correlation coefficient (ICC) were used to measure the internal consistency and test-retest reliability, respectively. Of the 169 informants assessed, 97 were retested. A Cronbach's +/- of 0.94 and an ICC of 0.92 were found. The reliability levels lead to the conclusion that the IQCODE-BR version is easy to comprehend. Satisfactory equivalence to the original version was observed.