The company will take care of the museum’s maintenance, rates, insurance, electricity, security and compliance costs over that period and will also put $20,000 a year towards attracting young people to join the local maritime society over the next 10 years.
Port Otago chief executive Kevin Winders said the agreement would help ensure the region’s maritime history was preserved.
"As the associated port, supporting our local museum is the right thing to do," he said.
"There are real treasures housed within that building, not to mention the role the historical society plays in our community."
Port Chalmers Historical Society president Brian McCormack said the museum was unique in New Zealand.
"It is prestigious for Port Otago to have the museum within its precinct," he said.
"We’ll be able to modernise how we present our collection, and we know that the collection will be preserved and be there for many years to come for visitors to enjoy and appreciate."
Historical society committee member Coral Kaan said the committee needed an injection of young people, "especially businesspeople with some business savvy".
"This agreement takes a financial burden off us and secures the viability of our museum for the future. And, for Port Otago, it’s a feather in their cap to be able to show off Port Chalmers’ maritime history."
Earlier in the year, Port Otago received resource consent to build a three-storey administration block, which will wrap around the museum.
Surrounding buildings and parts of buildings will need to be demolished to make way for the construction, including the boat shed addition to the museum and a 1920s outbuilding.
