The present research demonstrates that negotiators can act powerfully without having power. Researchers and practitioners advise people to obtain strong alternatives prior to negotiating to enhance their power. However, alternatives are not always readily available, often forcing negotiators to negotiate without much, or any, power. Building on research suggesting that subjective feelings of power and objective outcomes are disconnected and that mental simulation can increase individuals’ aspirations, we hypothesized that the mental imagery of a strong alternative could provide similar psychological benefits to having an actual alternative. Our studies demonstrate that imagining strong alternatives causes individuals to negotiate more ambitiously and provides them with a distributive advantage: negotiators reached more profitable agreements when they either had a strong tendency to think about better alternatives (Study 1) or when they were instructed to mentally simulate an attractive alternative (Studies 3-4). Mediation analyses suggest that mental simulation boosts performance because it increases negotiators’ aspirations which translate into more ambitious first offers (Studies 2-4), but only when the simulated alternative is attractive (Study 2b). Our findings further show that mental simulations are only beneficial when there is sufficient room in the negotiation to reach a profitable agreement, but backfire in settings where negotiators’ positions are difficult to reconcile (Study 5). An internal meta-analysis of the file-drawer produces effect size estimates free of publication bias and demonstrates the robustness of the effect. Our findings contribute to research on social power, negotiations, and mental simulation.