Sears impressed in recent short- and long-form series against Australia, but after an expensive tour of Pakistan has been edged by Henry, who will play at his first T20 World Cup at the age of 32.
"Matt has worked exceptionally hard on his skills across the phases of a T20 game to come back into selection consideration," coach Gary Stead said.
New Zealand will be led by Kane Williamson in the tournament, jointly hosted in the USA and the West Indies, with an otherwise steady-as-she-goes squad announced on Monday.
Emerging batter Rachin Ravindra is the only other man set to make his T20 tournament debut in a vastly experienced team.
Ravindra, power-hitter Finn Allen (both 24) and allrounder Glenn Phillips, 27, are the only squad members who will still be under the age of 30 on the day of the World Cup final.
Boult has played just twice for New Zealand in the past 18 months - an unimpressive two matches against Australia in February - but the T20 specialist has been selected for a likely swansong.
Kyle Jamieson (back) and Adam Milne (ankle) weren't considered due to injury, while Tim Seifert was overlooked.
Stead has included a clutch of spin options - specialists Mitchell Santner and Ish Sodhi as well as Phillips, Ravindra and Michael Bracewell - to be prepared for slow pitches.
Sears will travel as the team's reserve.
NEW ZEALAND T20 WORLD CUP SQUAD
Kane Williamson (capt), Finn Allen, Trent Boult, Michael Bracewell, Mark Chapman, Devon Conway, Lockie Ferguson, Matt Henry, Daryl Mitchell, Jimmy Neesham, Glenn Phillips, Rachin Ravindra, Mitchell Santner, Ish Sodhi, Tim Southee. Reserve: Ben Sears.
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