The announcement was made by Christie at a rally in Fortworth, Texas on Friday.
This has come as big boost for Trump who came under scathing attack from rivals ahead of the crucial "Super Tuesday".
"Donald is a leader. He is a successful person that, like me, isn't afraid to tell it like it is. Our system is broken and it won't be fixed from the inside. I am proud to offer my endorsement of his candidacy for President," said 53-year-old Christie.
Former White House contender Christie's endorsement to Trump just ahead of the 'Super Tuesday' in which primary elections would be held in 11 States is expected to what is supporters said "seal the deal" for the realty star-turned-politician.
"It is my great honour to receive the endorsement of the Governor. We have had a wonderful relationship for many years.
He is a solid person that I have tremendous respect for. I am really proud to receive the support of the Governor and his family," Trump said.
Trump, who has won three of the four Republican primaries, is leading in all but Texas State opinion polls, where he is having a close fight with his main rival Senator Ted Cruz. Notably, Trump has also been endorsed by Congressmen Chris Collins, Congressman Duncan Hunter, former Governor of Alaska Sarah Palin, South Carolina Lt Governor Henry McMaster, and Arizona Treasurer Jeff DeWitt.
Democratic National Committee National press secretary Mark Paustenbach said that Christie's endorsement is the best example yet that the GOP is the party of Trump.
"The Republican field just isn't serious and all its candidates have major problems heading into November. If anyone is wetting their pants, as Rubio suggested today, it's the Republican establishment.
This is yuuge," he said in a statement. Meanwhile, a leading Republican presidential candidate Marco Rubio launched a scathing attack on Trump describing him as a con artist and dangerous.
"Donald Trump is a con artist trying to hijack the conservative movement and the Republican Party, and he cannot be our nominee," Rubio said in an email to his supporters. Christie, a former federal prosecutor, is a moderate Republican running a largely Democratic state and was once seen as one of the party's best hopes in 2016.
OneIndia News (With agency inputs)