Up to 120 Red Funnel employees will strike over pay on July 27 and for 11 days in August.
Its average of 19 daily round trips from Southampton to Cowes will be reduced to 12 on these dates.
However, it stated that the strike action would have no effect on the Red Jet schedule because the service is scheduled to run as usual.
“We’re confident that we’ll be able to keep the Island connected and supplied as usual,” the company said in a statement.
It also stated that 50 percent of the dates between July 27 and August 29 would remain unchanged.
The walkouts have been scheduled for August 1, 3, 5, 9, 11, 15, 17, 19, 23, 26, and 29.
According to the Unite union, employees were unhappy with a 4.5 percent pay increase and had no choice but to strike.
Even with the offer increasing to 6.5 percent for the lowest paid, it was said to be “far below the real cost of living.”
The strike is expected to have an impact on the Cowes Week sailing regatta, which takes place from July 30 to August 6.
Red Funnel said it would “always endeavour” to prioritise passengers travelling for work, education, and essential medical appointments, as well as fuel, medical supplies, and food transportation.
Customers who have booked to travel on the days affected by the strikes should expect further communication from Red Funnel via text or email.
If you have a booking during the impacted date range and have not heard from us by 20 July, please contact us,” the company stated.