"I've seen the tweet about tapes. Lordy, I hope there are tapes," Comey told the Senate Intelligence Committee.
Comey was asked about his response to Trump's statement that he understood as a request that he drop the investigation into former national security advisor Michael Flynn. Some senators criticized him for not responding more forcefully to it.
Last month, Trump tweeted a suggestion that he had recorded their conversations, saying Comey "better hope that there are no 'tapes'" of the talks.
Comey testified before the Senate panel Thursday on the probe into Russian interference in the 2016 election. He talked about his relationship with Trump and the motives behind the president firing him, largely based on written records he kept after one-on-one meetings.