An official statement released on Friday said the loan agreement was signed on Thursday by Lebanese Finance Minister Fouad Sanyoura and the World Bank's director for Lebanon Joseph Saba.
The funds will be able to cover more than half of a $62 million project to rehabilitate the ancient city centres of Baalbeck, Byblos, Sidon, Tripoli and Tyre.
The cities are known for sites dating back to the Phoenician, Roman, Byzantine and Arab periods.
"The project considers Lebanon's cultural assets economic assests and integrates them into the life of the cities to boost economic development," Saba was quoted a saying.
Many of Lebanon's historic sites served as major tourist attractions before the outbreak of the civil war (1975-1990).
During the war years, they were left unattended and at times suffered damage.
A lack of government money has also exacerbated the problem.
The rest of the funds are to come from the French development agency, the Lebanese culture ministry, the Italian and Japanese governments and the UN Educational Scientific and Cultural Organisation, the statement said.
The loan is repayable over 15 years with a changing interest rate, based on the London Interbank Offered Rate, LIBOR and a six-year grace period.
Tourism was a major source of income for the Lebanese government before the war and the authorities are hoping to capitalise on the country's attractions to raise revenues.