The 299 migrants, who included 40 women and 19 children, were picked up early Tuesday in Mediterranean waters off the western city of Zliten, navy spokesman General Ayub Kacem said.
The migrants, of different African nationalities, were plucked from two rubber dinghies without engines and brought back to the Tripoli naval base, he said.
They were given food and medical attention before being transferred to a detention center, Kacem added.
Since the 2011 uprising that toppled longtime dictator Moamer Kadhafi, chaos-hit Libya has become a key point of departure for migrants heading to Europe.
Last month forces loyal to Libya's UN-backed unity government ousted a militia controlling the trafficking from the western city of Sabratha.
The United Nations last month said Libyan authorities were holding more than 14,500 migrants who had previously been kept captive by smugglers in farms, houses and warehouses in and around the coastal city.
The UN refugee agency said more than 20,000 migrants, including pregnant women and babies, were being held either in detention centers or by traffickers in Sabratha, warning of abuse "on a shocking scale".
Nearly 150,000 migrants have crossed the Mediterranean so far this year, according to the United Nations, and at least 2,826 others have died making the journey.
Hailing mainly from sub-Saharan countries, most migrants board boats operated by people traffickers in western Libya, and make for the Italian island of Lampedusa 300 kilometers (190 miles) away.
But migrant arrivals in Italy have dropped 69 percent since July, the European country said this week, as a deal with Libya blocks boats and would-be asylum seekers use other routes into Europe.
The number landing in Italy is down by 30 percent compared with last year, Italy's interior ministry said.
Arrivals in Spain, meanwhile, have more than tripled, with over 14,000 arrivals this year.