David Sherborne, for the Duke of Sussex, said MGN will pay Harry “a substantial additional sum by way of damages” as well as his legal costs.
The barrister said this included an interim payment towards the costs of £400,000.
In December, a judge ruled that phone hacking became “widespread and habitual” at MGN titles in the late 1990s and was practised “even to some extent” during the Leveson Inquiry into press standards in 2011.
Mr Justice Fancourt also concluded that Harry’s phone was hacked “to a modest extent” by MGN, awarding him £140,600 in damages.
Thirty-three articles in Harry’s claim were examined during the trial last year, with 15 articles found to have been the product of unlawful information gathering.
A further 115 articles were in his claim, which may have been the subject of a further trial.
In a statement MGN said: “We welcomed December’s judgment that gave the business the necessary clarity to move forward from events that took place many years ago.
“Where historical wrongdoing took place, we apologise unreservedly, have taken full responsibility and paid compensation.”
A spokesman for the publisher added: “We are pleased to have reached this agreement, which gives our business further clarity to move forward from events that took place many years ago and for which we have apologised.”
In a statement delivered by Mr Sherborne outside court, Harry said his “mission” over how the press operate continues."Everything we said was happening at Mirror Group was in fact happening, and indeed far worse as the Court ruled in its extremely damning judgement," Harry said.
"As the judge has said only this morning, we have uncovered and proved the shockingly dishonest way in which the Mirror acted for so many years, and then sought to conceal the truth."
He also launched another attack on Piers Morgan, the former editor of the Daily Mirror.
"In light of all this, we call again for the authorities to uphold the rule of law and to prove that no one is above it. That includes Mr Morgan, who as editor, knew perfectly well what was going on, as the judge held," his statement said.
Mr Morgan previously said in December after the judgement in the case he has "never hacked a phone or told anyone else to hack a phone".
Morgan later replied on X, formerly known as Twitter: “I totally agree with Prince Harry that ruthless intrusion into the private lives of the Royal Family for financial gain is utterly reprehensible… and I hope he stops doing it.”
Harry’s case at trial was heard alongside similar claims brought by actor Michael Turner, who is known professionally as Michael Le Vell and is most famous for playing Kevin Webster in Coronation Street, actress Nikki Sanderson, and Fiona Wightman, the ex-wife of comedian Paul Whitehouse.
The claims brought by Ms Sanderson and Ms Wightman were dismissed because they were made too late, despite the judge finding that some of their complaints were proved.
In his ruling on Friday, Mr Justice Fancourt ruled that Ms Sanderson and Ms Wightman should pay MGN the legal costs of defending their individual claims.
The judge also ruled that Mr Turner should pay MGN’s costs of responding to his claim from the date of March 5 2022, where an offer was made.
Roger Mallalieu KC, for MGN, previously said the publisher would be seeking interim payments from the trio – who are said to be insured for their adverse costs – of around £100,000 each.
Mr Justice Fancourt ruled that 90% of the interim payments should be made to MGN, with some deductions.