Partner notification (PN) is a public health strategy widely applied to control the spread of Sexually Transmitted Infections (STIs) by disrupting the transmission chain and by protecting against re-infection and health complications. Research suggests that individuals' own beliefs about the outcome of an action (outcome beliefs) and perceived ability to perform a specific behaviour (self-efficacy) influence intentions to notify sexual partner(s) for STI/HIV diagnoses. However, because HIV case management differs from other STI cases, there is a need to distinguish between PN related to STIs other than HIV and HIV. The present study aimed to examine the role of outcome beliefs and self-efficacy in predicting intentions to notify partner(s) separately of possible STI and HIV diagnoses. Participants were 177 adults (28.4 years, ± 9.04) who completed self-report measures of self-efficacy, outcome beliefs related to PN and PN intentions for STI and HIV diagnoses. Hierarchical regression models showed that self-efficacy was a significant unique predictor of intentions to notify sexual partners for STIs other than HIV after controlling for outcome beliefs, F (3, 174) = 9.82, p < 0.001. However, this was not evident for intentions to notify partners for HIV. These findings indicate that self-efficacy plays an important role in predicting intentions of notifying sexual partner (s) for STI diagnosis but not for HIV diagnosis. Given that self-efficacy has been successfully integrated in the delivery of education programmes aimed at promoting positive health behaviours, our findings suggest that it could be also incorporated into school-based sex education programmes.