Aim To assess the criterion validity of the Brazilian version of the Informant Questionnaire on Cognitive Decline on the Elderly (IQCODE‐BR), and analyze the influence of educational level and age of both the elderly and the informants on the questionnaire scores. Method The study design was a cross‐sectional study with a convenience sample. Convergent validity was assessed using the Mini‐Mental State Examination, and the accuracy of the IQCODE‐BR was evaluated by receiver operating characteristic curve analysis. Multivariate logistic regression analysis was carried out to determine the influence of sociodemographic characteristics on IQCODE‐BR scores. Results A total of 169 elderly individuals participated in the study, of which 35.5% were diagnosed with dementia. There was no statistically significant association between the IQCODE‐BR scores, and the age and educational level of both the elderly and the informants. The cut‐off point for greater accuracy was 3.52, with sensitivity of 83.3% and specificity of 80.7%. The area under the receiver operating characteristic curve was 0.83 (95% CI 0.766–0.893). There was a negative and moderate correlation between IQCODE‐BR and the Mini‐Mental State Examination scores (P < 0.01). Conclusion This study suggests that the IQCODE‐BR is a valid tool for screening of dementia and that IQCODE‐BR scores do not seem to be influenced by age, educational level and other factors associated with the informants. However, further studies are required to evaluate informant characteristics, such as anxiety states, depression and burden level. Geriatr Gerontol Int 2013; 13: 687–693.