His promise came after a summit between him and North Korean leader Kim Jong Un in which Mr Kim committed to complete denuclearisation and he offered unspecified "security guarantees" to North Korea.
In a press conference after the historic agreement was made, the US President was asked if the fate of Christians was involved in the talks with the secretive state's leader.
Mr Trump assured said Christians were brought up in the discussion and "things will be happening".
He replied to the reporter: "It will be worked on. Christians, yes. We brought it up. Franklin Graham spent and spends a tremendous amount of time in North Korea. He has it close to his heart. It did come up and things will be happening. Great question."
The US leader said he was prepared "to start a new history" and "write a new chapter" between the two nations, declaring: "Real change is indeed possible."
John Choi, which isn't his real name, is a Christian who managed to escape North Korea.
He told Premier's News Hour that the summit brought him hope that things will improve for Christians in the country because they have been increasingly getting worse.
He believes Mr Kim will make improvements because the North Korean leader wants the benefits of a better economy that comes with the historic agreement.
"Kim knows how many years starvation has been ongoing... this man does understand what is going on inside the country and how many years he can sustain without any reform...without denuclearisation there will be no economic opportunity."
The World Watch List by Open Doors has repeatedly ranked North Korea the country where persecution against believers is worst.
Choi said Christians are detained in prison camps, are being used for chemical weapons tests and have been publically executed for their faith.
"People trying to escape from North Korea to the outside, it's getting more difficult nowadays because there are very strict surveillance and security on the border.
"You have no freedom to say anything and you have to follow the leader as God and it's very difficult to hear about other religions, Christianity or any type of religion in the world."
However, he said he continues to have hope for his home country.
"If I can see a very beautiful church in my hometown one day, that is going to be implicated by freedom of expression, opportunity, and freedom of North Korea. We don't know yet how it will work. I believe God makes things that are impossible, possible."
Listen to John Choi speaking with Premier's Tola Mbakwe here:
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