Damascus opened an embassy in the Lebanese capital, Beirut, last year but has not yet named an ambassador.
"We have raised the Syrian flag over our mission in Lebanon and very soon we will name an ambassador for Lebanon," Walid al-Moualem, the Syrian foreign minister, said on Monday.
The thaw between the two neighbours came after a joint pledge in Paris by Bashar al-Assad, the Syrian president, and Michel Sleiman, his Lebanese counterpart, to work towards better relations.
The two countries have also agreed to demarcate the border between them, but a committee to work on the issue has been slow in starting work.
Many Lebanese politicians have blamed Damascus for the killing of al-Hariri and a United Nations investigation inmplicated a numbeer of Syrian officials. Damascus has repeatedly denied the accusations.
The two countries have not had diplomatic relations since Britain and France created them from the remnants of the Ottoman Empire after the first world war.
They both gained independence from France in the 1940s.