Associated British Ports (ABP) Southampton has acquired Eling Wharf to secure the key role the historic wharf plays in supporting the Port of Southampton.
The 16.6-hectare site, which sits next to the A35 roadway and is predominantly used for storage, is home to 24 tenants running a variety of businesses.
In medieval times the wharf was used for shipbuilding, but it has been occupied by a chemical works and coal importers in recent times.
ABP Southampton Director Alastair Welch said boundary fencing and security would be improved.
"Port users have increasingly relied on Eling Wharf to support their operations as the port has become busier," said Mr Welch.
"As we progressively enhance the site over the next five years, we will work with the council to explore longer-term options for Eling Wharf."
ABP Southampton is the UK's first port for export, handling on average 14 million tonnes of commodities each year. It is also the first cruise port, with more than two million passengers each year.