The Duke of Cambridge has met survivors of the Christchurch mosque attacks, in which 50 people were killed in March.
The duke also met some of the officers and medics who were among the first at the scene of the shootings.
He got a traditional Maori greeting from New Zealand's PM Jacinda Arden at the start of his two-day tour.
Meanwhile, the Duke of Sussex, who will soon become a new father, joined the Duchess of Cambridge at an Anzac Day service at Westminster Abbey.
Anzac Day marks the anniversary of the first major military action fought by the Australian and New Zealand Army Corps (Anzac) in World War One.
Prince William performed a hongi with Ms Ardern as he was welcomed in Auckland, before attending a service there.
He also met four-year-old Alen Alsati - who was injured in the attack and awoke from a coma earlier this week - at Starship Children's Hospital.
The Duke of Cambridge meets five year old Alen Alsati, who is recovering in Starship Children’s Hospital in Auckland after being injured in the Christchurch mosques terrorist attack.— Kensington Palace (@KensingtonRoyal) April 25, 2019
Alen woke from a coma earlier this week after suffering critical injuries in the attack. pic.twitter.com/XcNAsIw7xt
He then travelled to Christchurch, where he asked officers and medics about how they had put their training into practice.
"Nothing really trains you for seeing it in real life", said the duke, who has spent time as a pilot with the air ambulance service in East Anglia.
"I'm sure the team pulls together," he said.
New Zealand police commissioner Mike Bush said the "emotion was palpable" during the visit and the duke was concerned with how those involved were coping a month on from the attacks.
"His main piece of advice was to talk to each other, to not bottle things up - to support each other to talk about what they saw and what they do afterwards," he said.
At the police headquarters, dozens of messages from the people of Christchurch were pinned up along the corridors, thanking officers for their work after the shootings.
Among them was a card that said: "You never give up and you never ever will give up trying to save NZ."
Later, the prince had a private meeting with Muslim community leaders, thanking them for bringing the community together after the tragedy.
Prince William is travelling on behalf of the Queen at the request of Ms Ardern.
She said the visit would "bring comfort" as the duke had a "close connection" with New Zealand and Christchurch in particular.
"His visit provides the opportunity to pay tribute to those affected by the mosque terrorist attacks and show support to the local and national community," she said.
William offered prayers for the Christchurch community and described the attacks as a "cruel nightmare".
It is not the first time he has visited Christchurch in the wake of a tragedy.
In 2011, he attended a memorial service after an earthquake killed 185 people.
In a speech that day, he said: "My grandmother once said that grief is the price we pay for love. Here today, we love and we grieve."
The Duke and the Duchess of Cambridge also visited New Zealand in 2014, on their first official tour.
On Thursday afternoon, the Duchess of Cambridge was accompanied by her brother-in-law, the Duke of Sussex, at an Anzac Day Service at Westminster Abbey in central London.
The Dean of Westminster prayed for an "end to terror and for the triumph of peace" as he remembered the terror attack on New Zealand's mosques.
Prince Harry had not been confirmed for the royal engagement until the last minute as his wife, the Duchess of Sussex, is due to give birth to their first child soon.
A relaxed-looking Harry and Catherine were pictured laughing and chatting as they entered the abbey.
Previously, Meghan has revealed the baby is due at the end of April or the start of May - but it's not known whether she is expecting a boy or a girl.