English, who was the sole contender for the job, announced Social Housing Minister Paula Bennett as the deputy leader, following a special caucus meeting of the ruling center-right National Party.
English, who will be sworn in later in the day, has already lined up senior cabinet minister Steven Joyce, the minister for economic development, to replace him in the finance ministry.
He is expected to announce further cabinet changes in the coming weeks and has also signaled a "stocktake" on policy.
"I am both excited and humbled by this opportunity," English, who comes from a conservative, Catholic family in New Zealand's south, told reporters after the meeting.
English, who 13 years ago oversaw a disastrous election loss for the National Party to the center-left Labour Party, takes the reins of a country in good economic shape compared to much of the developed world.