The meeting took place at an undisclosed location and discussed "the dangers to the Palestinian cause" including "Arab plans for normalisation" with Israel.
Leaders of Lebanon's Hezbollah movement and the Palestinian Hamas group, both sworn enemies of Israel, have met to discuss diplomatic normalisation between the Jewish state and Arab countries, the movement said.
On Sunday, Hamas political chief Ismail Haniyeh was given a hero's welcome at Ain al Helweh, Lebanon's largest Palestinian refugee camp.
Hezbollah-run Al Manar TV reported earlier that Hassan Nasrallah, head of the Iran-backed Shia Hezbollah movement, and Haniyeh stressed the "stability" of the "axis of resistance" against Israel.
They discussed "political and military developments in Palestine, Lebanon and the region" and "the dangers to the Palestinian cause" including "Arab plans for normalisation" with Israel, Al Manar said.
It reported the meeting without specifying where or when it took place.
Nasrallah has been living in secret locations since Hezbollah's devastating 2006 war with Israel and makes rare public appearances. He said in 2014 that he often changes his place of residence.
The Haniyeh-Nasrallah meeting follows an August 13 announcement that the Jewish state and the United Arab Emirates (UAE) have agreed to normalise ties.
While the US-led diplomatic drive aims to boost a regional alliance against Iran, Palestinians have condemned it as a "stab in the back" by an Arab country as they remain under occupation and don't have their own state.
Israeli Prime Minister Benjamin Netanyahu has said his country is in talks with other Arab and Muslim leaders now about normalising relations, following the deals with UAE and, decades ago, Egypt and Jordan.
Haniyeh arrived in Lebanon on Wednesday, on his first visit to the country in nearly 30 years, for direct and video-conference talks with other Palestinian groups that oppose Israel's diplomatic initiative.
Haniyeh, who heads the political bureau of Hamas, the group that controls the Gaza Strip, was triumphantly carried on the back of a man wearing a mask into Ain al Helweh, under the protection of Hamas members and camp guards.
Before a cheering crowd of hundreds in Ain al Helweh, near the southern coastal city of Sidon, including refugees who travelled to see him from other camps, Haniyeh praised his movement's military capacity and shrugged off the UAE-Israel normalisation.
"Not long ago, our rockets only reached (targets) metres from Gaza's borders. Today, the resistance in Gaza possesses rockets that can reach Tel Aviv and beyond Tel Aviv," he said.
As for normalisation between Israel and Arab countries, that "does not represent the people, neither their conscience, nor their history nor their heritage," Haniyeh said, according to a Hamas statement.
Israel's military has in recent weeks targeted Hamas in the Gaza Strip and what it says have been Hezbollah gunmen along its northern border with Lebanon.
It also regularly launches air strikes in war-torn Syria against what it says are Hezbollah and other pro-Iranian militants fighting on the side of Syrian Bashar al Assad's regime.