Possessing social power leads to approach-related affect and behavior, whereas lacking power leads to inhibition (Keltner, Gruenfeld, & Anderson, Psychol Rev 110:265-284, 2003). However, such effects should be moderated by whether an explanation is given for these power differences. Participants were assigned to a low-power or high-power role and then interacted with a confederate in the opposite role. Participants were told these role assignments were made for legitimate (expertise) or illegitimate (nepotism) reasons, or were given no explanation. High-power participants showed more approach-related affect and behavior and reported less dissonance than low-power participants, but many of these effects were moderated by the presence versus absence of an explanation. When no explanation for power differences was provided, high-power participants exhibited more approach-related behavior than low-power participants but also felt more guilt and unease. Implications for system justification theory and the literature on social power are discussed.