Maronite Patriarch Beshara Rai arrived in Damascus on Saturday to attend the enthronement of Syria's Greek Orthodox leader, Yuhanna X Yazigi, Syrian state television said.
The Lebanese National News Agency meanwhile reported that Rai would hold mass at the Maronite cathedral in Damascus later in the evening.
The ceremony for the new Greek Orthodox leader is to be held at 8:30 am (0630 GMT) on Sunday at the Church of the Holy Cross in Qassaa, a central neighbourhood of the conflict-hit Syrian capital.
Rai's visit to Syria will be the first visit by a Maronite patriarch since independence in 1943, Lebanon's anti-Syrian regime newspaper An-Nahar reported.
"The participation of several church leaders is a way to express solidarity between churches while Syria is in crisis, a crisis for Christians in Syria," the daily added.
Lebanese President Michel Sleiman conveyed support for the visit.
"I support the visit. It is the patriarch's duty to evaluate the needs of Christians and it is not appropriate for the head of state to tell him what he can and cannot do," Sleiman said in a statement.
"Not everything is linked with politics. Patriarch Rai, like Patriarch Yazigi, is aware of the needs of Christians and how to act to maintain their roots in this land," he added.
Christians represent about five percent of the population in Syria, where rebels and forces loyal to President Bashar al-Assad are locked in a civil war the UN says has killed more than 60,000 people.
Rai was elected in March 2011 as the 77th patriarch of Lebanon's Maronites, the country's largest Christian community which makes up about one third of the four-million population and from which the president hails.
In January, Rai strongly denounced states that provide money, weapons and other assistance to both the Assad regime and its opponents, saying they would have to answer "crimes before the court of history".
Yuhanna X Yazigi was chosen as the Patriarch of Antioch and All the East on December 17, replacing Ignatius IV Hazim who died earlier in the same month.
Many of Syria's Christians have remained neutral in the country's conflict. Others have taken Assad's side, for fear of the rise of Islamism.