Local police announced on Saturday the New Zealand pilot had been freed after more than one and a-half years in captivity in West Papua, Indonesia.
The armed faction of the West Papua National Liberation Army kidnapped Mehrtens in February 2023 after he landed a small commercial plane in a remote, mountainous area.
The family released a statement via the Ministry of Foreign Affairs and Trade today, thanking a number of those involved in his release and asking for privacy as he recovered.
"The last 19 and a-half months have been very difficult for all of us, and we give our heartfelt thanks to our friends, family and community for their love and kindness during this time.
"There were so many people involved in the effort to find and release Phil ... but we are extremely grateful to the Indonesian government - including the Indonesian police and Indonesian military - for prioritising peaceful negotiations in order to keep Phil safe."
The family said they were also grateful the army allowed Mehrtens to get "several messages" out to them during his time in captivity.
"Those messages filled our souls and gave us hope and that we would eventually see Phil again."
The Mehrtens family said there would be "forever" grateful to the New Zealand government and police, the New Zealand embassy in Jakarta, Hostage International and Susi Air for their "incredible" support and care.
"The team at MFAT and the Embassy, in particular, went above and beyond from the minute Phil was taken.
"We are so grateful for the trust they placed in us and the daily updates they provided. As challenging as this has been, it would have been inordinately harder if we were not aware of how hard everyone was working and what actions were being taken.
"Seeing how diligently and caringly they serve the people of this country makes us incredibly proud to be Kiwis."
The family thanked the New Zealand media "for showing restraint and sensitivity" during Mehrtens time in Papua and asked for privacy "so he can adjust to life after captivity".
"Phillip has been through a long and arduous ordeal, and he now needs time and space to recover."
Negotiations had stumbled - West Papua Action Aotearoa
West Papua Action Aotearoa spokesperson Catherine Delahunty said it was a relief Mehrtens was freed before Indonesia's new president took power.
Indonesia's new president Prabowo Subianto will be sworn in on October 20.
Delahunty, a former Green MP, said previous negotiations had stumbled and it was a relief they had finally reached a peaceful solution.
"This has been such a long and difficult ordeal for him and his family. We're all really worried about whether it would be possible. Getting him free was a series of very delicate negotiations," she said.
"Many of them have started and stumbled and not led to anything. It's a great relief that he is free. And I think one of the things that was important to people over there is they really wanted to get this resolved before the new president of Indonesia, who he has a terrible reputation associated with his military career before he became president. And they have achieved that.
"And as far as I know, there was no bloodshed."
