Abstract Objective To assess the prevalence of and factors associated with suicidal behavior in patients seen at the emergency department (ED) of a general hospital in southern Brazil. Method Descriptive, observational, cross-sectional study. The records of all patients who had an emergency psychiatric consultation at the ED conducted by the emergency psychiatric consultation service at Hospital São Lucas da Pontifícia Universidade Católica do Rio Grande do Sul in 2016 and 2017 were analyzed and stratified by sex and by age groups (15-29 years, 30-49 years, 50-69 years, and 70 years and older). Suicidal behavior was characterized by factors such as thoughts of death, suicidal thoughts, and suicidal risk. Suicidal behavior was compared by sex and between age groups with chi-square tests. Multivariate analysis of suicidal behavior and gender, age, and specific diagnoses were compared with Poisson regression. Results A total of 1,172 records from January 2016 to December 2017 were examined. There were more ED visits by females (63.1%) than males. Younger patients (15-29 years) had a higher severe risk of suicide than elderly (≥ 70 years) patients (54.1 vs. 19%; p < 0.01). Indicators of suicide behavior stratified by sex and by age group revealed marked differences between age groups for all variables among female patients. Overall, age group patterns for males were very similar in terms of suicidal behavior variables. Conclusions A high prevalence of suicidal behavior was observed in this sample, particularly among young adults and especially associated with female gender and diagnoses of depression and personality disorders.