He had already dropped a bombshell even before he walked into the Senate hearing on Thursday and his next act certainly generated headlines.
Mr Comey seems convinced Donald Trump interfered with the FBI’s investigation into Russia’s meddling with the US election.
He also seems to think the US President is a liar.
They are explosive allegations, but they raise more questions than they answer.
Marc Kaskowitz, Mr Trump’s personal lawyer, launched a swift and scathing attack.
He depicted the ex-FBI boss as someone hell bent on undermining the President, who lied about his encounters with the Mr Trump, and who could face sanctions for “leaking”.
Expect that narrative to be repeated.
The Republican National Committee has already sent round a memo of talking points to fight Mr Comey.
Among them – Mr Trump feels totally vindicated; the testimony confirmed he, Mr Trump, wasn’t under investigation; and Mr Trump sacked Mr Comey for the good of the country, even though he knew it could be detrimental to his presidency.
They’ve already scripted the narrative – Mr Comey is as a man of contradictions and he lost the confidence of both Republicans and Democrats. In other words, he can’t be believed.
But some – including James Risch, the Republican Senator from Idaho – praised Mr Comey’s clarity and detail.
Democrats went much further, sounding the alarm and expressing deep concern about Mr Trump.
The top Democrat on the House Intelligence Committee, Adam Schiff, said in a statement: “Former FBI Director Comey’s written testimony confirms a host of troubling allegations concerning the President’s conduct.”
Despite so many uncertainties, and plenty of conjecture, there were still some fascinating revelations.
We learned that Mr Comey was deeply wounded by the way he lost his job as FBI chief.
And that he leaked the memo about his dinner with Mr Trump to a friend because he thought it would result in the appointment of a Special Counsel.
But the former FBI director also admitted he wasn’t very brave when, he alleges, the President asked him to ease off the probe into Michael Flynn, Mr Trump’s former national security adviser.
Mr Comey didn’t, he said, have the “presence of mind” or the courage to tell the President his request was inappropriate.
Overall, the former FBI chief was careful and damning with his words. Known as a teller of memorable tales, he has just ensured this one is far from over.
And lordy, it could take a long time to reach any conclusion. This was not a hearing that included a smoking gun.