This study examines the impact of a single science museum visit on the science self-efficacy (SSE) of emerging adult learners. Building upon previous research, which showed a significant short-term impact of a museum visit on SSE, our study aims to replicate these findings and gain deeper insights into the underlying mechanisms contributing to increased SSE. In the present study, we implemented a randomized control trial design and hired a recruitment firm to ensure a representative sample through quota sampling. Participants were randomly assigned to either visit a museum (Treatment) or see a movie (Control). In addition to visiting their assigned excursion, participants completed pre-, post-, and delayed-post-surveys and a virtual interview. Results demonstrate that visiting a science museum had a significant positive short-term impact on SSE. Moreover, the museum visit led to an increase in SSE by broadening visitors' perceptions of what counted as science. Although no significant longer-term impact on SSE was observed, participants who visited the museum maintained a broadened view of science even 3 months later. Interviews further revealed that positive performance interpretations during the museum visit, which were often achieved by participants exploring conceptually-accessible, hands-on exhibits at their own pace, played a vital role in enhancing SSE. Participants also described how the museum visit broadened their view of science by connecting science and daily activities. Implications of these findings for informal science education practitioners and directions for future research are discussed.