BackgroundHuman immunodeficiency virus (HIV) infection is a public health concern worldwide. The clinical manifestations include underweight and oral lesions. The objective of this study was to assess the relationship between oral pathologies and underweight among HIV-positive patients in Yaounde, Cameroon. MethodsWe conducted a cross-sectional study between February 1st and 30th June 2021 at Yaounde Central Hospital in Cameroon. A total of 205 HIV positive patients aged at least 18 years were recruited via consecutive sampling. The questionnaire consisted of sociodemographic information, anthropometric data, dietary habits, HIV history and treatment and oral examination data. The data were analysed with R software. Multivariate analysis was used to assess the risk of being underweight among HIV-positive patients with oral pathologies. A p value < 0.05 was considered to indicate statistical significance. ResultsThe prevalence of oral pathologies was 52.7% (95% CI: 45.6-59.6), and the main pathologies were candidiasis (40.5%, 95% CI: 33.7-47.5) and linear erythema (32.2%, 95% CI: 25.9-39.1). The prevalence of underweight was 20% (95% CI: 14.88-26.26). Binary logistic regression revealed that HIV-positive patients with oral pathologies were 10.89 (95% CI: 2.28-16.63) times more likely to be underweight than were HIV positive and AIDS patients without oral pathologies (p = 0.002). ConclusionOral candidiasis and linear erythema were common in HIV positive and AIDS patients. HIV-positive and AIDS patients with these oral pathologies were at higher risk of being underweight than were those without oral pathologies. The effective medical care of these patients must include oral and nutritional management.