A Kiwibank spokesperson said the 19 staff affected by the change were offered roles in their branches or nearby outlets and two employees had chosen redundancies.
Napier will operate as a stand-alone Kiwibank branch from May 10 and Hastings from May 17.
New Zealand Post head of retail Mark Yagmich said the organisation was committed to keeping postal services in the area.
"We know this will be a change in how some of our customers access postal services in the Hawke's Bay, but we are determined to stay in the community.
"We have worked with local businesses like this in other places and it works well for us, the businesses we partner with, and also for the local community."
Yagmich said New Zealand Post had been working with Paper Plus outlets who were now ready to take up the extra postal needs of the community.
"We also hope people will enjoy the longer opening hours Paper Plus offers, including being open on Sundays."
Janice Beaumont of Paper Plus Hastings and Napier said both outlets had been providing postal services to the area for more than five years and had knowledgeable and trained staff.
"We've been selling our customers stamps and helping them with their postal needs for over five years now, and our staff know what they are doing.
"We think our customers really enjoy the convenience of our longer opening hours, and being able to shop for stationery, books and magazines at the same time as posting their mail."
Paper Plus Hastings is open from 9am to 5pm weekdays, 9am to 7pm Saturday and 10am to 2pm Sunday.
Paper Plus Napier is open from 9am to 5pm weekdays, 9am to 4pm Saturday and 10am to 2pm Sunday.