The capture of the hospital was a boost for the rebels, who only the day before saw 20 of their fighters killed in an al-Qaida suicide car bombing in the northern city of Darkoush, said the British-based Syrian Observatory for Human Rights.
It also underscores the intensity of the rebel infighting that has raged for days between Syrian rebels and their one-time allies, fighters from the extremist Islamic State in Iraq and the Levant.
The two main rebel camps in Syria fighting against President Bashar Assad's troops a chaotic array of rebel brigades and the al-Qaida-linked group turned their guns on each other last Friday. The clashes have since become the most serious rebel infighting since the uprising against Assad began in March 2011.
The rebel-on-rebel fighting began after tensions, which had simmered for months, erupted into the open after reports that the al-Qaida fighters had tortured and killed a popular doctor.
The clashes add another layer of complexity to the Syrian conflict, less than three weeks ahead of a planned international peace conference to try to resolve the civil war.
Syrian rebels seized the hospital in Aleppo's Qadi Askar quarter that the al-Qaida fighters had overrun months ago and used as their main compound or base for the area, said the Observatory, which relies on a network of activists on the ground.