A new cafe will open at a seafront tourist attraction in spring this year.
Yellow Kite has agreed to enter into an agreement for a lease while installing a cafe in the western courtyard of Southsea Castle.
The firm will also build a semi-permanent marquee in the castle's eastern courtyard.
The company, which aims to serve healthy food to the castle's visitors, and will re-invest its profits into the cafe, and local community centres offering healthy catering services across Portsmouth.
When the work at the castle is finished, subject to English Heritage consent, Yellow Kite and Portsmouth City Council will sign a 10-year lease for the firm to operate the cafe.
And the council will also be able to use the venue as a place which can be booked for weddings or other events.
It is expected to open when the castle re-opens to the public in April this year.
The firm was appointed as the council's preferred operator after its decision last February to place the flagship healthy eating venue at the castle