Introduction: This study aimed to identify factors associated with late diagnosis and clinically monitor newly diagnosed HIV/AIDS patients. Method: Retrospective longitudinal study, based on secondary data from a specialized unit at a tertiary hospital. Data collection included sociodemographic, behavioral, clinical, and laboratory data of newly diagnosed HIV patients between 2015-2019. Data analysis adopted inferential statistical tests using the SPSS program, considering α ≤ 0.05. Results: 314 individuals were newly diagnosed with HIV/AIDS. 70.3% (208) had a late diagnosis, and 57.1% (169) were diagnosed very late. There was an association of the very late diagnosis with the variables sex and education and with origin, entry, occurrence of opportunistic diseases, use of ARV therapy, and death, associated with late and very late diagnosis, respectively. The results of the regression model indicate that males had 2.28 [95% CI 1.11 - 4.46] higher chances of having a late diagnosis compared to females. Conclusions: This study evidenced a high prevalence of late and very late diagnoses in newly diagnosed male HIV patients who presented with opportunistic diseases, requiring hospitalization, and having a significant risk of progressing to death.