Samir Kassir, a 45-year-old newspaper columnist, was killed on Thursday when a bomb exploded under his car in the Christian Beirut district of Ashrafieh.
Lebanon's opposition, which blamed Syria and its local allies for the killing, asked government officials not to attend the funeral.
Hundreds of people watched as Kassir's coffin was carried from the offices of his newspaper, An-Nahar, in Beirut's downtown Martyrs' Square, by pallbearers including the newspaper's director-general, Gibran Tueini.
Mourners threw rose petals on the coffin as it made its way to a nearby Greek Orthodox church for Kassir's funeral.
Among mourners was Kassir's wife, journalist Giselle Khoury, a journalist with Al-Arabiya television, who had demanded an international investigation into her husband's death. Kassir held French and Lebanese citizenship.
Lebanon's anti-Syrian opposition, which has demanded for months that pro-Syrian President Emile Lahoud resign, called for demonstrators to gather near the presidential palace on Monday.
Opposition leader Elias Atallah said the protesters would lay a wreath "that clearly points to the direct responsibility of this security regime". Lahoud has condemned the killing of Kassir.
Opposition accuses Syria
Syria pulled all its troops out of Lebanon in April after three decades, and Lebanon is in the midst of a four-round parliamentary election that the anti-Syrian opposition hopes will end Damascus' control of the legislature.
On Friday, about 200 journalists and politicians - many holding black pens to symbolize freedom of expression - stood for an hour in Martyrs' Square in silent tribute to Kassir, as bells tolled in nearby churches.
Opposition spokesmen blamed Syria for the assassination - a charge Syria denied - and accused Damascus of continuing to interfere in Lebanon's politics.