The accident occurred just before departure from the port at 10 a.m., according to a press release from Eckerölinjen.
No injuries were reported.
The ferry M/S Eckerö, which operates the Grisslehamn-Åland route, suffered minor damage above the waterline, but none of the ships were taking on water and no oil spills were detected, according to Eckerölinjen.
"We are currently preparing the repair of M/S Eckerö, in dialogue with the Swedish Transport Agency," the shipping company writes in a press release.
The cause of the accident is unknown. Traffic will resume on Thursday, according to schedule.
