Abstract Sexual behavior change is a complex issue influenced by complex variables, intrinsic and extrinsic. This study aimed to assess factors influencing actual use of a male condom among secondary school students in southern Tanzania. In all, 227 sexually experienced participants aged 14 to 18 completed a pretested questionnaire. Out of 227 sexually active participants, 120 (53%) reported consistent condom use and (62.5%) had multiple sexual partnerships. Of 120 who reported condom use, 42 (35%) had tested for HIV. Among males, age was positively correlated with actual condom use, while being a Catholic and having multiple concurrent sexual partners were negatively correlated with actual condom use. Among females, being a Protestant was positively related with actual condom use, while being a Catholic, reporting multiple sexual partnerships, and perceived barriers to condom were negatively correlated with actual condom use. In conclusion, sexually active youth in this population practice risky sexual behaviors, with a low proportion of condom use. Efforts are warranted to motivate sexually active youth to engage in HIV prevention, including condom use and HIV testing. Keywords Tanzania, Health Belief Model, HIV testing, sexual active, youth