Port owner Portsmouth City Council has launched a tender process to promote the facility, which represents a gateway to Britain but faces difficult trading conditions with Europe.
A tender document seen by PRWeek reveals that the work is expected to be worth around £150,000 a year, and will last at least three years with a possible two-year extension.
Launching in May, it will cover PR, advertising, marketing and digital services.
The port posted 2012-13 trading revenues of £15.8m, down on the previous year, and its annual report pointed to "a reduction in the volumes of trade" brought about by continuing problems in Europe.
Between 2008 and 2012, passenger numbers also dipped from 2.1 million to just under 2 million a year.