The United States imposed sanctions on Thursday on Lebanese businessman Ali Youssef Charara and his Beirut-based telecommunications company Spectrum Investment Group Holding for providing support to Hezbollah.
It is the first application of a law President Barack Obama signed in December which makes it easier to target the financial sources of the group.
Charara has received millions of dollars from Hezbollah to invest in commercial projects that financially support the group, the US Treasury Department said in a statement.
The sanctions freeze assets of Charara and Spectrum - which provides telecommunications services in the Middle East, Africa and Europe - in the US, and prohibit Americans from doing business with them.
Hezbollah, a Shiite political and militia group in Lebanon which is backed by Iran and supports the Assad regime in Syria, has long been labelled as a terrorist organization by the United States.
The new law, called the Hezbollah International Financing Prevention Act of 2015, strengthened US authorities' ability to target Hezbollah and threatened consequences for those who help the group, the Treasury Department said.
"Hezbollah relies upon accomplices in the business community to place, manage and launder its terrorist funds," Adam Szubin from the Department said in a statement.
"We are committed to exposing and disrupting these networks to pressure Hezbollah's finances and degrade its ability to foment violence in Lebanon, Syria and across the region," Szubin said.