Blackstone held talks to buy NCR outright earlier this year, but could not agree on terms, people familiar with the matter told Reuters in September.
NCR, whose shares were up 4 percent in premarket trading, said it would use the investment to speed up its transformation into a software and services company and to help fund a share buyback of up to $1 billion.
Duluth, Georgia-based NCR, which was founded more than a century ago, has been trying to expand into the software sector.
It recently launched a cloud-based software system for ATMs called Kalpana that is meant to replace outdated PC software on the machines and help owners cut costs.
In the year up to Wednesday's close of $26.78, NCR's shares had dropped more than 6 percent, and its shareholders have been pressuring the company to explore options, including a sale.
The Wall Street Journal first reported the Blackstone would buy a stake in NCR on Wednesday.