Mr Trump told ABC News he would consult Defense Secretary James Mattis and CIA director Mike Pompeo about what could be done legally to combat radicalism.
The president said while radical groups beheaded people in the Middle East “we’re not playing on an even field”.
However, ex-CIA director Leon Panetta said it would be a “serious mistake to take a backward step” on torture.
Mr Trump said he wanted to “keep our country safe”.
“When they’re shooting, when they’re chopping off the heads of our people and other people, when they’re chopping off the heads of people because they happen to be a Christian in the Middle East, when Isis is doing things that nobody has ever heard of since Medieval times, would I feel strongly about waterboarding?” he said.
“I have spoken with people at the highest level of intelligence and I asked them the question ‘Does it work? Does torture work?’ and the answer was ‘Yes, absolutely’.
He continued: “They chop them off and they put them on camera and send them all over the world. So we have that and we’re not allowed to do anything?
“I will rely on Pompeo and Mattis and my group and if they don’t want to do it that’s fine. If they do want to do then I will work toward that end.
“I want to do everything within the bounds of what you’re allowed to do legally but do I feel it works? Absolutely I feel it works.”
Mr Trump indicated in a TV debate during the Republican presidential race that he might order troops to carry out waterboarding “and tougher” on terrorism suspects.
But he later softened his stance, saying he would not order the military to break international law.
Waterboarding is the practice of pouring water over someone’s face to mimic drowning as an interrogation tactic.
It is widely considered as a form of torture and has been banned by the US.
Mr Panetta told the 100 Days programme on BBC World News: “The reality is we really don’t need to use enhanced interrogation in order to get the information that is required.
“General Mattis believes that, others in the intelligence business believe that, and the FBI believes that, so I think it would be a mistake to go back to that.
“I think it could be damaging in terms of our image to the rest of the world.”