Harm-minimisation strategies aim to reduce gambling-related risks; however, minimal evidence supports the effectiveness of current strategies involving the placement of warning signs in gambling venues and on electronic gaming machines (EGMs). This qualitative replication study evaluated the differential effect of pop-up messages compared to static signs, and the content of messages on EGMs on recall, thoughts and behaviours assessed during the session and at two-week follow-up. In study one, 127 regular EGM gamblers (male = 97, mean age = 20.3) recruited from a university student population attended a laboratory where they were randomly assigned to play a computerbased simulated EGM analogue displaying signs that differed by (a) mode of presentation (pop-up and static) and (b) message content (informative, self-appraisal, and control/blank). In study two, an identical methodology was used but carried out in an invivo gaming setting with 124 regular EGM players (male = 81, mean age = 44.1). Results from both studies showed that pop-up messages were recalled more effectively than static messages immediately and at two-week follow-up. Pop-up messages reportedly had a significantly greater impact on within-session thoughts and behaviors. Messages encouraging self-appraisal resulted in significantly greater effect on self-reported thoughts and behaviors during both the experimental session and in subsequent EGM play. These findings support the effectiveness of pop-up messages containing selfappraisal messages as an appropriate harm-minimisation initiative.