(1) Background: Several opportunities have appeared for the dissemination of culture and heritage thanks in part to the widespread use of information and communications technologies. Virtual museums have appeared as innovative technological products but often lack an evaluation of the impact that they have and their success in achieving their purpose. In this sense, this work seeks to evaluate the impact of a virtual museum on users’ attitudes toward cultural heritage. (2) Methods: We used a factorial design of 2 (direction of thoughts: positive vs. negative) × 2 (presence level: high vs. low) × 2 (virtual museum vs. interactive website). (3) Results: Attitudes toward heritage can change as a function of a multimedia experience, thought favorability, and presence. In a virtual museum, when general attitudes are evaluated, a sense of high psychological presence reduces the effect that thoughts (especially when negative) have on attitudes. However, in the case of visiting an interactive website, the effect of the direction of thoughts on attitudes occurred regardless of conditions of high or low presence. Similar tendencies are observed for specific attitudinal objects. (4) Conclusion: A virtual museum can have different effects depending on the interaction of important variables from the virtual reality literature and not only the classic main effects. Recommendations for interventions and future practical and theoretical work are presented.