Carnival UK, the parent company for P&O Cruises and Cunard, will remain at Carnival House on Harbour Parade until 2038.
The cruise company has re-negotiated the lease on the four storey building, prominent on West Quay Road, to ensure that Southampton will be its home for at least another 19 years.
Carnival House, owned by Aviva Investors' Lime Property Fund, is home to more than 1,200 employees, the majority of whom are from the Hampshire area.
"With a fleet of ten ships, the majority of which home port in Southampton throughout the year and three new ships on order to arrive by 2022 we continue to invest in the city, the port and its infrastructure to secure our long term future," said Carnival UK president Josh Weinstein.
He added: "Each time a ship comes into Southampton it brings £2m to the area and we have around 180 turnarounds next year. Also, local provenance is a high priority and we use many Hampshire and Dorset suppliers of quality food products and services across our ships."
"Our association with Southampton is a vital one and I am delighted that we have secured our place here for such an extended amount of time. How fitting that even this process was Southampton-focused, as we partnered with two local companies to achieve this extension to our lease. I would like to thank Tim Burbidge and Stephen Baker from Womble Bond Dickinson and also David Ferriman from Realest who worked hard on our behalf."
Source: Insider Media Limited