Mr Davis, of Ngati Manu descent, spent 20 years in the education field before he was selected as the Labour candidate for Te Tai Tokerau electorate in 2008.
He said his new position would give him a stronger say on Northland issues.
"The higher up the ladder you are, the more influence you have," he said.
"I'm going to have to support Jacinda Ardern as the Labour Party leader and get out there and lift the profile and encourage people to party vote Labour. So there will be some more focus there but hopefully that will be made up for by the influence I'll be able to do in this position."
Mr Davis, and the rest of Labour's Maori electorate MPs opted not to run on the party list, as part of a strategy to defeat the Maori Party and Mana alliance at the general election.
Mr Davis said while he would prefer to stay off the list, constitutionally the Labour leader and deputy have the top two spots.
He was not worried his new position might mean voters would elect Mana Movement leader Hone Harawira as a way of ensuring both get in to Parliament.
"I think people will see that here's an opportunity for Tai Tokerau to have the deputy Prime Minister," he said.
Mr Harawira said he was not interested in "point scoring" and wanted to congratulate Mr Davis.
"There will be challenges for him to come, no doubt a number of them will be coming from me. But today's an important day for Kelvin and I wish him all the best."
Mr Harawira said he had not given much thought to the idea that people might vote for him over Mr Davis so both would get to the Beehive.
"A two for one, it's worked before there's no reason why it can't work again," he said.
Mr Davis' elevation to deputy leader is just one more achievement for a successful family.
Mr Davis is one of four children born to Panapa and Glenys Davis of Kawakawa.
The eldest, Patrick, is a senior sergeant who is second in charge of Northland police iwi liaison. His other brother, Greg, is a district court judge, while his sister Sonya Davis-Brooking, the youngest in the family, is a teacher in Auckland.
His mother was feeling "a little bit overwhelmed" yesterday.
"It's not something we were expecting - I don't know if he was expecting it - but we're very proud of him, as we are of all our kids."
Frank Leadley, Mr Davis' former principal at Bay of Islands' College, was " extremely proud".
"He was involved in all school activities, a prefect, a very good member of the First XV and academically sound. He was a very good all-round student."
Mr Leadley put Mr Davis' success down to a supportive family.
Mr Davis' last school role was as principal of Kaitaia Intermediate.
Board of Trustees chairman Kevin Matthews said the school had "every right to feel immensely proud that it has a past principal who's deputy of the opposition".
"He was very good for the school. He was forward thinking and he initiated quite big changes," Mr Matthews said.
"Our school is just under 80 per cent Maori and he definitely changed the culture, especially among the boys. The school was a bit of a hard place prior to that. By the time left the school was in a very good position."
