Al-Qaeda's Syria branch claimed responsibility for the attack in the Jabal Mohsen Alawite neighborhood.
"Nine people were killed and 37 others wounded," the health ministry said in a statement.
"The first suicide bomber entered into the Ashqar cafe at around 7:30 pm (1730 GMT) and blew himself up," a security source told AFP.
Panicked survivors tried to flee the scene of the attack, said the source, who spoke on condition of anonymity.
"Then, a second suicide attacker arrived, and blew himself up too," he said, updating his initial account of a single suicide bomber.
Lebanese security forces believe the bombers lived in Mankubeen, a majority Sunni neighborhood just 500 meters (yards) away from Jabal Mohsen.
The security source said the army had cordoned off the bombers' homes. A man who was lightly wounded said he was near the scene of the blast when the attackers struck.
"I was at the cafe with other people, when we suddenly heard a first blast," Zuheir al-Sheikh said.
"Then we heard a huge blast, though I have no idea what caused it," he added.
Al-Qaeda's branch in Syria, the Al-Nusra Front, claimed responsibility for the blasts via Twitter.
The Arab Democratic Party is the main group representing the Alawite minority in Lebanon.