The second round of talks center around the formation of a transitional governmental body and the cessation of violence.
The opposition delegation said each side would meet with Brahimi separately until the U.N. envoy decided there was common ground for joint discussions.
The first round of talks ended some 10 days ago, with no firm agreements and bitter statements from both sides.
The government insists that the talks focus on fighting "terrorism" -- its description of the uprising -- but the opposition says the priority should be the removal of President Bashar al-Assad.
The opposition has insisted that the government commit in writing to the 2012 Geneva I communique, which called for the formation of a transitional government.
Al-Assad's government has ruled out any transfer of power.
Brahimi will meet with high-level Russian and U.S. diplomats in Geneva this week, the U.N. said Monday.
He will meet with Russian Deputy Minister of Foreign Affairs Gennady Gatilov and U.S. Under Secretary of State Wendy Sherman on Friday, the U.N. said without providing more details.
In a separate development, the Organisation for the Prohibition of Chemical Weapons announced a third shipment of chemical weapons material from Syria had taken place.
It said the material was on board a Norwegian cargo vessel accompanied by a naval escort from China, Denmark, Norway, and Russia.
"In-country destruction of some chemical materials has taken place alongside the removal of chemical weapons material," it added.