English says he wants to be a positive Prime Minister for New Zealand.
"I think that we're a country that's matured in many ways since the very difficult period we had in the late 80s and early 90s," he said.
"I want to be a PM where New Zealanders feel they can flourish here, not just some of them but all of them."
English admitted his stance remains firmly against euthanasia and abortion but admitted he would change his vote on same sex marriage if he had his time again now.
He was proud to stand alongside Bennett as his deputy, who made the journey to the second most powerful office in the nation from being a solo teen mum.
She is just the first female deputy leader of the National Party and just the second female deputy prime minister.
Key earlier said today was a day for reflecting on happy memories.
"It's a beautiful day and it's a great day for a new Prime Minister so I'll be looking forward to signing off with my Caucus colleagues as the leader after 10 years at the top leading the National Party and eight years the country," Key said heading into the meeting.
"But I know I'm passing over to tremendously good hands in the form of Bill English and Paula Bennett and they're going to steer the country extremely well."
Despite initial competition from Health Minister Jonathan Coleman and Police Minister Judith Collins, English was left last man standing in the race, which ended just days after Key shocked the nation with his resignation.
Both stood down on Thursday after it became clear the 54-year-old finance minister had the backing of the majority of the 59-member caucus.
Collins says she doesn't expect to be punished for her failed bid at the leadership, nor does Simon Bridges who is hopeful for a continued role in cabinet.
The Transport Minister on Saturday withdrew his own bid to be deputy, clearing the way for fifth ranked Bennett to be elected unopposed.
He said the new leaders were "spoilt for choice" with those around them.
English has already revealed senior Cabinet minister Steven Joyce will replace him as finance minister.
There are expected to be more tweaks to come in terms of cabinet and policy.
"We'll use it as an opportunity for a stocktake and we'll see how that looks in January, February," he said.
