Haftar's forces had pounded the airbase on previous days and surrounded fighters from the Third Force militia.
"Our forces... took full control of Tamenhant airbase in the south of Libya," said Khalifa al-Obeidi, spokesman of Haftar's self-proclaimed Libyan National Army.
An LNA officer, who declined to be named, said Haftar's forces had pounded the airbase on previous days and surrounded fighters from the Third Force militia.
Haftar's forces persuaded the fighters to evacuate the airbase, which they did, allowing the LNA to take over the facility without any resistance, said the officer.
The Third Force is loyal to the UN-backed Government of National Accord not recognised by the LNA.
Last week Third Force fighters attacked Brak al-Shati airbase, also in southern Libya, which is controlled by Haftar forces, killing 140 people, including civilians.
The attack was condemned by the United Nations, the European Union and the GNA.
The United Nations and Human Rights Watch said summary executions may have taken place at Brak al-Shati.
The unity government, the rival administration in eastern Libya and their respective backers are battling for influence in the North African country, which has been wracked by chaos since the fall of dictator Moamer Kadhafi in 2011.
The LNA does not recognise the authority of the GNA, and instead supports the rival authorities based in the east.