Objective To assess the prevalence and associated factors of self‐reported halitosis in institutionalized adolescents in a city in southern Brazil. Methods This cross‐sectional study involved male institutionalized adolescents, aged 15–19 years old, at the Socio‐Educational Assistance Center in the city of Passo Fundo, Brazil. Data collection was performed by a research team composed of two interviewers, two clinical examiners of oral health and two examiners of salivary flow. A structured questionnaire was applied, which included demographical, socioeconomical, general health behaviour, presence of health problems and oral health self‐perception variables. Decayed, Missing, Filled Index was used for the clinical examination. The salivary flow collection was performed using the mechanically stimulated total saliva method, in which only the liquid component was measured. Results The prevalence of self‐reported halitosis in this sample was 51.5% (n = 35). In the final multivariate analysis, halitosis was significantly associated with the non‐white racial group (prevalence ratio [RP]:1.703; 95% confidence interval [95%CI]:1.101–2.634), use of crack (RP:1.857; 95%CI:1.270–2.714) and number of decayed teeth (PR: 1.123; 95%CI:1.008–1.252). The use of alcohol and access to dental care in the last 12 months were not significantly associated with self‐reported halitosis. Conclusion It was concluded that non‐white and crack‐user youngsters had a high occurrence of self‐reported halitosis. Higher rates of dental caries are also associated with halitosis.