Badruddin Haqqani is the son of network founder Jalaluddin Haqqani and the brother of Nasiruddin and Sirajuddin Haqqani, all of whom are "specially designated global terrorists" under a US executive order and subject to US and United Nations sanctions.
The network has been blamed for some of the deadliest anti-US attacks in Afghanistan, including a suicide attack at a US base in Khost in 2009 that killed seven CIA operatives.
"As a result of the designation, all property subject to US jurisdiction in which Badruddin Haqqani has any interest is blocked and US persons are prohibited from engaging in any transactions with him," the State Department said in a statement.
"This action will help stem the flow of financial and other assistance to this dangerous individual."
The statement said Badruddin Haqqani "is an operational commander for the Haqqani network," which "has been at the forefront of insurgent activity in Afghanistan, responsible for many high profile attacks."
Washington has accused the group of several kidnappings including that of New York Times reporter David Rohde in November 2008. He escaped in June 2009.
The Haqqani network is an al-Qaeda allied group run by Afghan warlord Sirajuddin Haqqani and based in Pakistan's North Waziristan tribal district.