STEAM Packet staff will be campaigning outside sittings of the House of Keys and Tynwald this month.
They fear a rival freight service by Mezeron could affect Steam Packet jobs and passenger services.
On Saturday concerned staff handed out flyers to shoppers in Douglas about "the threat to ferry services".
Since Mezeron launched a daily freight service from Douglas to Liverpool the Steam Packet Company and its employees have been raising concerns about the impact it could have.
Unions RMT, Nautilus and Unite are representing Steam Packet staff.
Chris Bowen, chief officer of the Ben-my-Chree who is also the union liasion officer for Nautilus, said the campaign will continue through the coming weeks.
Flyers were handed out on Saturday at the Villa Marina where a TravelWatch meeting was taking place, Tesco - which is using the Mezeron freight service - and in Douglas town centre.
Also see: Steam Packet staff begin campaign