The event, which started Friday, celebrates the maritime industry and helps raise money for charities in Waldo County.
Some of the weekend's activities included a regatta, a lobster lunch fundraiser, live music, and a boat building challenge.
Event organizers said a new world record was set by two locals, who were able to build a boat in less than an hour and a half, beating their own record.
Organizers said Belfast Harborfest has something for everyone.
"The reason we did so many things in one event was kind of to celebrate the maritime tradition in Belfast and along the Penobscot Bay, and to just give something back to the community," said Duke Marston, the chair for Belfast Harborfest. He said the event is to "show the community something where they can all get together and have fun."
Marston said he thinks they raised about $4,000 for the Waldo County YMCA at one of the weekend's fundraisers.
He said plans for next year's festival are already in the works.