Henri Bergson's philosophy, which Sartre studied as a student, had a profound but largely neglected influence on his thinking. In this paper I focus on the new light that recognition of this influence throws on Sartre's central argument about the relationship between negation and nothingness in his Being and Nothingness. Sartre's argument is in part a response to Bergson's dismissive, eliminativist account of nothingness in Creative Evolution (1907): the objections to the concept of nothingness with which Sartre engages are precisely those raised by Bergson. Even if Sartre's account of nothingness in its entirety is found to be flawed, I argue that the points he makes specifically against Bergson are powerful. My discussion concludes with a brief examination of the wider philosophical background to Sartre's and Bergson's discussion of nothingness: here I point to some important aspects of Sartre's early philosophy, including some features of his conception of nothingness, that may testify to Bergson's positive influence on his thought.