But he said a third case was also under investigation, and slammed the American embassy in Beirut as a "den of spies."
"When the Israeli enemy failed to infiltrate Hezbollah, it turned to the most powerful intelligence agency," he said in a closed-circuit television speech, referring to the CIA.
"Our investigation has found that... (CIA) intelligence officers have recruited two of our members separately, whom we shall not name out of respect for the privacy of their families.
"The first confessed he was recruited five months ago... while the second confessed he had been recruited even before that," he said, adding that the recruiters were CIA agents posing as diplomats at the US embassy east of Beirut.
Nasrallah also said the group was investigating whether the third member of the militant group had been recruited by the CIA, Israel's Mossad or the intelligence service of a European country.
A US embassy spokesperson told AFP there was no substance to Nasrallah's accusations, pointing instead to internal problems within Hezbollah.
"These are the same kinds of empty accusations that we have repeatedly heard from Hezbollah," the US spokesperson said shortly after Nasrallah's speech.
"There is no substance to his accusation," he added. "It appears as if Nasrallah was addressing internal problems within Hezbollah with which we have nothing to do.
"Our position towards Hezbollah is well known and has not changed."
The United States blacklists Hezbollah as a terrorist organisation.
Nasrallah warned that Hezbollah, which prides itself on the discipline of its members and its immunity to infiltration, was facing a new threat.
"A new confrontation has now begun," he said. "We were already in a state of confrontation with the Israeli enemy, but now we are being targeted by US intelligence, opening a new front in our struggle."
The Shiite leader insisted, however, that the alleged agents had not been involved in the 2008 assassination of senior Hezbollah operative Imad Mughnieh in the Syrian capital Damascus.
Hezbollah openly accused Israel of being behind the bombing that killed Mughnieh and vowed to avenge his death. The Jewish state denied responsibility.
More than 100 people in Lebanon have been arrested on suspicion of spying for Israel since April 2009, including military personnel and telecommunications employees.
Lebanon and Israel technically remain in a state of war and convicted spies face life imprisonment or the death sentence if found guilty of contributing to Lebanese loss of life.
Lebanon has protested to the United Nations over the alleged spy networks.
Syrian- and Iranian-backed Hezbollah last fought a devastating war with Israel in 2006.
The month-long conflict killed more than 1,200 Lebanese, mainly civilians, and 160 Israelis, mainly soldiers, and destroyed much of Lebanon's major infrastructure.