For My Father's Kingdom is directed by Pacific film-makers Vea Mafile'o of Tonga and Samoa's Jeremiah Tauamiti.
The documentary centres on Vea's father, Saia Mafile'o, and his four children.
Film reviewer Chris Schulz told Kathryn Ryan on Nine to Noon people were in tears at the screening in Auckland.
"All great documentaries shine a light on something that you don't know anything about. Right?
"So, this is about tithing in the Tongan church. I knew nothing about this.
"When I walked in, I walked in absolutely cold. And it really affected me.
"It's full of stuff that kind of gets to you. It gets really emotional. It's quite a raw documentary."
Mr Schulz said while For My Father's Kingdom is heartfelt and emotional, it is also very funny.
For My Father's Kingdom questions the cost to preserve one's culture and faith in the diaspora.
Driven by his deep faith in God and Tongan culture, pensioner Saia Mafile'o navigates not only the rough streets of South Auckland, but also his sometimes-fraught relationship with his children who struggle to accept their father's commitment to a kingdom that tore their family apart.
Saia Mafile'o surrenders all his income to the Wesleyan Church of Tonga's Misinale - the fundraising campaign that calls on people in and from Tonga to raise money for the community.
Saia Mafile'o lives in New Zealand but adheres to this tradition.
This becomes difficult for his children to understand because their father's tithing means the family is short of money for other things.
But a journey to the homeland helps them understand the Tongan way of life.
The children also accept that attitudes in New Zealand are not always compatible with Western notions of efficiency.
The film explores how the church, the Tongan culture and traditions can hold a family together, but it can also be a burden.
For My Father's Kingdom has just completed screenings in Auckland and is showing in Wellington this week before moving on to regional New Zealand.