The group said the sale of the 36.5 percent stake will enable it "to further focus on the development and growth of its core businesses".
It said the completion of the deal is expected in the second quarter of 2018, "subject to necessary approvals".
The two groups set up the consumer healthcare joint venture in 2015 following a major reorganization of the Swiss group's drugs portfolio.
The split marks the first major transaction since Vas Narasimhan succeeded Joe Jimenez as chief executive last month.
"While our consumer healthcare joint venture with GSK is progressing well, the time is right for Novartis to divest a non-core asset at an attractive price," Narasimhan was quoted as saying in a company statement.
"This will strengthen our ability to allocate capital to grow our core businesses, drive shareholder returns, and execute value creating bolt-on acquisitions as we continue to build the leading medicines company, powered by digital and data."
The 2015 deal gave Novartis the right to offload the joint venture to GSK beginning this month.
GSK said the new agreement will allow it to move forward with strategic planning.
"Most importantly it also removes uncertainty and allows us to plan use of our capital for other priorities, especially pharmaceuticals" reasearch and development, GSK's chief executive Emma Walmsley said in a statement.
Novartis in January reported that strong sales of two of its main blockbuster drugs enabled it to turn in a "good operational performance" in 2017.
Net profit climbed by 15 percent to $7.7 billion in 2017 on a one percent increase in sales to $49.1 billion.
GlaxoSmithKline's net profits jumped 70 percent to £1.5 billion ($2.1 billion, 1.7 billion euros) last year on bumper sales.