A statement by the alTawheed Brigade said the rebels "fully liberated" the facility in Aleppo on Saturday. It was posted on al-Tawheed's website on Sunday and said the Islamist rebel brigade's commander was killed in the battle.
The complex, known as Hanano Barracks, includes an army base, a recruiting center, and a military school.
The al-Tawheed Brigade is one of the largest rebel groups operating in Aleppo, a major front in the civil war since July.
One of the videos on the group's website shows the body of a man the narrator says is "the hero and martyr who was killed on the day of liberating the infantry school," apparently the al-Tawheed commander, Col. Youssef al-Jader. A boy said to be the commander's son is seen crying as he leans over the dead man.
Another video shows several rebels praying at the captured base. Armed fighters are also seen walking around the infantry school, its walls bearing the slogan "Assad Forever" and pictures of Assad and his late father, Hafez. The Assad family has ruled Syria for more than 40 years.
In a related development, Egypt said Sunday that it had evacuated more than 4,000 of its nationals from Syria in recent months. The Foreign Ministry statement did not give further details.
Also Sunday, Iran put forward a six-point plan to end the Syrian civil war, including negotiations, presidential elections, and a halt to arms shipments. This came during a two-day meeting in Tehran of 200 representatives of Syrian communities, but no prominent rebels. The rebels are unlikely to relate to the plan, as they refuse to talk with Assad and consider Iran unqualified to mediate because of its support of the regime.