Previous research suggests that the established link of vertical position and self-assignment of social power affects the processing of social exclusion. We hypothesized that verticality-induced self-assignment of social power moderates the evaluation of exclusion via a change in subjective expectancy of social participation. Following this idea, a superior position-associated with higher power-was supposed to increase the sensitivity for a transition to social exclusion. The transition was simulated in a virtual ball tossing game (cyberball): an inclusionary block was followed by partial exclusion of the participant. The participants' vertical position relative to the co-players was varied in three experimental groups (superior vs. even vs. inferior). From inclusion to partial exclusion, we observed an increase of an event-related brain potential related to the violation of subjective expectancy (P3), and participants reported a corresponding increase in threat to social needs and negative mood. For participants at inferior position exclusionary effects on both, P3 and need threat, were less pronounced as compared to participants at even or superior position. These results indicate that verticality impacts basic cognitive processes of subjective expectancy formation. An inferior position already provides a bias for the loss of social power, and the transition to social exclusion is less unexpected.