Terror management theory (TMT) posits that people cope with mortality concerns via symbolic immortality (e.g., secular cultural beliefs that outlast death) and/or literal immortality (afterlife belief). However, what happens when these two forms of immortality conflict, as in atheism? Would atheists' mortality concerns be better assuaged by affirming an afterlife, or by affirming their literal immortality-denying worldview? Drawing on an untested TMT hypothesis, we predicted that atheists would be buffered from mortality concerns if their atheistic worldview - no life after death - was challenged, but not if it was supported. Results confirmed the hypothesis and were also found for theists and agnostics. These findings support TMT's claim that literal immortality is of paramount importance in ameliorating death concerns.