Hamas, which controls the Gaza Strip, was one of Mr Al Assad's closest allies but left Syria in 2012 after condemning his government's brutal suppression of peaceful protests in March 2011, which triggered the country's descent into civil war.
“The Hamas delegation arrived in Damascus on a two-day visit,” during which the Palestinian faction will meet Mr Al Assad, said Palestinian Popular Struggle Front leader Khaled Abdel Majid.
The meeting will be followed by a news conference.
The visit by the delegation, led by Arab relations chief Khalil Al Hayya, comes after the hardline group signed a reconciliation deal with its Palestinian rival Fatah in Algiers last week, vowing to hold elections by next October in an attempt to settle a 15-year rift.
It also comes after Hamas announced that it wanted to normalise relations with Damascus, citing “rapid regional and international developments surrounding our cause and our nation”.
Analysts said that was a reference to the growing number of Arab governments that have normalised ties with Hamas's arch-enemy Israel in recent years.
A Hamas leader told AFP that the group planned to reopen its Damascus office but said it was “too early” to talk about relocating its headquarters to the Syrian capital.
The thaw in relations between Hamas and Damascus was brokered by Tehran and Lebanese militant group Hezbollah, a senior Hamas source said.
Over the past decade, Syrian officials had accused Hamas of betrayal.
The group has its origins in the transnational Muslim Brotherhood, whose Syrian branch was one of the leading factions in the armed opposition after the civil war broke out.
Hamas officials have said they severed ties with the Brotherhood in 2017.