CBRE Inc., the exclusive agent for the owner, Southshore Group Partners Inc., is listing the almost 495,000-square-foot office building.
No listing price was given in an opportunity statement that is available online. The building's 2012 certified taxable value was almost $28.6 million.
Southshore bought the property for $39 million in 2004 from OAIC Jax LLC, which bought the building in 1998 for $36 million from Prudential Insurance Co. of America, according to Duval County property records.
The riverfront building was developed for Prudential Insurance Co., which now occupies a nearby structure built in 1985.
Aetna Inc. bought the Prudential HealthCare business from Prudential in 1999 and consolidated operations at the tower.
The offering statement, dated 2013, says the building is 98 percent leased to 13 tenants, including four major health care related tenants that take up more than 85 percent of the property.
Major tenants include Aetna, Baptist Health System, University of Florida Health Jacksonville and Medical Services Co.
Prudential's decision to establish its Southeastern regional office in Jacksonville led to city leaders calling Jacksonville "the Hartford of the South," reflecting a status as an insurance center, and generated more development along the Southbank of the St. Johns River.
A 1998 report in The Florida Times-Union explained that Prudential was selling the glass-and-marble structure to Ocwen Asset Investment Corp., or OAIC. The building is 22 floors high but counts 20 for leasing purposes.
In August, the Daily Record reported that South Shore Group Partners LLC is moving its management office within the building and that the structure was fully leased for the first time in 15 years.
Betsy Reichert, vice president of operations and property manager, said in August the management offices were relocating because its existing space is being leased by an expanding tenant.
"I've been here since 1998 and our building is 100 percent leased," she said.
The opportunity statement, listed under CBRE's capital markets-investment properties, lists Jacksonville brokers Michael Harrell and Louis Nutter, both senior vice presidents, and William Moylan Jr., an executive vice president and partner in Boston.
Moylan heads the CBRE capital markets team in New England.
The opportunity statement calls the property a "Class A landmark office and medical office building in Downtown Jacksonville."
"Excellent amenities, low vacancy and strong fundamentals make the Aetna Building an outstanding source of both immediate and long term cash flow," with a year-one net operating income of $5 million.
It states it has a parking ratio of 5.14 spaces for 1,000 square feet of space.
"Rarely does a single Class A investment combine a protected Downtown waterfront location, demographic trends that outpace the nation in multiples, and unparalleled industry froth for its tenants."
Information is available at cbremarketplace.com/aetnabuilding.
CBRE declined comment. Reickert was not immediately available Tuesday morning.
The Aetna Building, a 20-story Southbank tower often heralded as the tallest building in Florida when it was developed in 1955, is for sale.