Objectives To evaluate the prevalence of HIV-related misconceptions in an outpatient centre of Kinshasa (Democratic Republic of Congo) and analyse the association between these beliefs and HIV infection. Methods A case–control study was carried out from December 2010 until June 2012. We assessed 1630 participants aged 15–49 attending a primary outpatient centre in Kinshasa: 762 HIV Voluntary Counselling and Testing attendees and 868 blood donors. A 59-item questionnaire about knowledge, attitudes and practice was administered during a face-to-face interview, followed by an HIV test. Cases and controls were respondents with a newly diagnosed HIV-positive or HIV-negative test, respectively. Unconditional logistic regression was used to analyse the association between misconceptions and HIV seropositivity. Results 274 cases and 1340 controls were recruited. Cases were more likely than controls to have a low socioeconomic status, no education, to be divorced/separated or widowed. An association was found between the following variables and HIV seropositivity: having a poor HIV knowledge (adjusted OR=2.79; 95% CI 1.43 to 5.45), not knowing a virus is the cause of AIDS (adjusted OR=2.03; 95% CI 1.38 to 2.98) and reporting more than three HIV-transmission-related misconceptions (adjusted OR=3.30; 95% CI 1.64 to 6.64), such as thinking an HIV-positive person cannot look healthy and that HIV is transmitted by sorcery, God’s punishment, a kiss on the mouth, mosquitoes, coughs/sneezes or undercooked food. Conclusions Despite having access to healthcare services, there are still many people in Kinshasa that have HIV-related misconceptions that increase their HIV risk. Our findings underscore the need for a culturally adapted and gender-orientated basic HIV information into Congolese HIV prevention programmes.