The plant, to be developed by Fukang Technology, will be located in the northern province of Bac Giang and will annually produce eight million units, the government said in a statement on its website.
Foxconn has so far invested $1.5 billion in Vietnam and plans to raise its investment by $700 million and recruit 10,000 more local workers this year, the government said.
Separately, state media reported last week Foxconn was also looking into investing $1.3 billion in Thanh Hoa province, 160 km (99.42 miles) south of Hanoi.
Foxconn is moving some iPad and MacBook assembly to Vietnam from China at the request of Apple Inc, a person with knowledge of the plan said in November, as the U.S. firm diversifies production to minimise the impact of Sino-U.S. trade tensions.
Foxconn did not immediately respond to an email seeking comment.
(Reporting by Khanh Vu; Editing by Ed Davies)
By Khanh Vu