It was the second tour in Afghanistan for Harry, 27, who will start flying missions within 10 days in the country's restive Helmand province, the British military said. In 2007-08, he served in Helmand as an air traffic controller.
Looking relaxed if slightly tired, Harry gave a thumbs-up Friday after a long journey on a troop carrier flight from England to Britain's Camp Bastion, a sprawling desert base near the southern Afghan town of Lashkar Gah.
Capt. Harry Wales, as he is known in the military, wore his combat uniform and joined his 100-strong unit - the 662 Squadron, 3 Regiment Army Air Corps.
As part of the Apache's two-man crew, Harry will be both a co-pilot and the gunner responsible for firing the Apache's wing-mounted aerial rockets, Hellfire laser-guided missiles and 30mm machine gun.
Britain has around 9,500 troops in Afghanistan, mainly based in Helmand province, and has suffered 425 deaths since the start of operations there in 2001.
"Prince Harry, like any soldier, considers it a great honor to represent his country in her majesty's armed forces wherever it chooses to deploy him," St James's Palace said in a statement.
Harry did not speak as he arrived in Helmand, and was not expected to comment publicly on his work for several weeks.
The prince's previous posting as a battlefield air traffic controller in Afghanistan in late 2007 and early 2008 lasted only 10 weeks. It was cut short after his deployment was made public.
Britain's defense ministry had asked the news media not to report information surrounding the prince's deployment, saying the publicity could put him and his colleagues in greater danger, but an Australian magazine not aware of the agreement broke the news. It was picked up by both the Drudge Report website and a German publication.
With his typical humor, Harry joked at the time about his nickname "the bullet magnet." His job was to direct attack helicopters and fighter jets to targets on the ground.
But with that time in Afghanistan, Harry became the first member of the British royal family to serve in a war zone since his uncle, Prince Andrew, flew as a helicopter pilot in the 1982 Falklands war with Argentina.
Next Saturday, the prince will celebrate his 28th birthday at Camp Bastion - but he won't be able to raise a toast with one of his beloved cocktails. The desert compound, which is next door to the U.S. military's Camp Leatherneck base, is an alcohol-free zone.
Before leaving for Afghanistan, Harry said farewell to his immediate family at Queen Elizabeth II's private estate in Scotland, Balmoral, and stopped to see his brother Prince William at his Kensington Palace home in London earlier this week.
St James's Palace said Prince Charles was "immensely proud of his son" and he and the queen had been briefed on the details of Harry's deployment.
Harry was met Friday at Camp Bastion by Royal Navy Capt. Jock Gordon, commander of the Joint Aviation Group.
"Working alongside his colleagues in the squadron, he will be in a difficult and demanding job," Gordon said.
Britain's defense ministry decided to confirm Harry's deployment this time after a threat assessment concluded that making the details public would not put Harry or his colleagues at any additional risk.
In an interview last March, Harry insisted he was eager to return to combat after training to fly Apache helicopters, including at U.S. bases in California and southern Arizona.
"I've served my country. I enjoyed it because I was with my friends. And, you know, everyone has a part to play," he told CBS News.
"You can't train people and then not put them into the role they need to play. For me personally, as I said, I want to serve my country. I've done it once, and I'm still in the Army, I feel as though I should get the opportunity to do it again," he said then.
In May 2007, the British military prevented Harry from heading out on a planned six-month tour of duty to Iraq because the risks to his safety were deemed too great.