"I think Boris would do a very good job," Trump said in an interview with The Sun, published on Saturday. Trump's comments came ahead of his state visit to the UK, which begins on Monday.
Johnson as well as Foreign Secretary Jeremy Hunt and Home Secretary Sajid Javid are in the race to become the next Tory leader and head of the government after Prime Minister Theresa May announced recently that she would be stepping down on June 7.
As the UK braces for the US President's visit, Trump said he had been paying close attention to the Tory leadership contest.
"I actually have studied it very hard. I know the different players. I think Boris would do a very good job. I think he would be excellent. I like him. I have always liked him. I don't know that he is going to be chosen, but I think he is a very good guy, a very talented person," Trump said.
Remarking that other candidates had asked him for endorsements, the US President said, "I could help anybody if I endorse them." He, however, did not name Tory leaders who sought "his support", but said he looked favourably on Hunt saying "I like him".
Trump's comments came as UK's Home Secretary Sajid Javid became the latest leadership contender to say he was prepared to leave the EU with no deal.
Having previously said he was "surprised how badly" Brexit negotiations went, Trump told the Sun the UK "allowed the European Union to have all the cards". "It is very hard to play well when one side has all the advantage," he said, adding the negotiators failed to put pressure on the EU.
The process to elect the next British Prime Minister is expected to continue till July as lawmakers will take part in several rounds of voting until a decisive result emerges.
The UK is on course to leave the EU on October 31 following years of negotiations with the EU. With May failing to get her deal passed through Parliament, it was unclear weather the UK would be leaving the bloc with a deal or not.
( With inputs from IANS )