Problem drinking and gambling are addictive behaviours experienced by young adults and commonly occur with narcissism. Research has acknowledged two distinct forms of narcissism: grandiose and vulnerable. There has been work that has examined the relationship between grandiose and vulnerable narcissism and addictive behaviours, but it has been limited, particularly with vulnerable narcissism. Evidence suggests vulnerable narcissism, but not grandiose narcissism, is associated with greater negative affect. Accordingly, shame, a potent social emotion could be a mediator in the narcissism-addiction pathway. Shame has been implicated in both vulnerable narcissism and problem drinking and gambling. Thus, we hypothesized that shame would mediate the relationship between vulnerable narcissism and addictive behaviours. Young adults (N = 210) completed self-report baseline (Time 1) and 1-month follow-up (Time 2) assessments of shame, narcissism, problem drinking, and gambling. As predicted, those with elevated vulnerable narcissism at Time 1 had increased shame at Time 2, which predicted problem drinking and gambling at Time 2. This relationship was not observed for grandiose narcissism. Overall, our results suggest that feelings of shame are essential to understanding the vulnerable narcissism-addiction pathway, and an important consideration when designing clinical interventions for at-risk young adults.