An aide said al-Hariri returned to Beirut on Saturday night, three days before Lebanon marked the first anniversary of the assassination of his father, Rafiq al-Hariri, the former prime minister of Lebanon.
Al-Hariri left Lebanon in late July and weeks later said a plot to kill him had been uncovered.
He spent most of his time in France and in Saudi Arabia, meeting the leaders of both countries.
Al-Hariri also held talks last month with George Bush, the US president, in Washington.
A UN inquiry into his father's assassination on 14 February last year has implicated Syrian security officials and their Lebanese allies in the murder.
After the murder, large demonstrations in Lebanon prompted Syria to bow to international pressure and end its 29-year military presence in Lebanon in April.
Saad al-Hariri led an anti-Syrian coalition to victory in parliamentary elections in May and June.
He has demanded that those responsible for his father's death be brought to justice and he remains a fierce critic of Damascus.
Syria denies any role in the assassination of al-Hariri.