The Kishorn yard in Wester Ross was one of the largest dry docks in Europe, employing about 3,000 people.
Welsh marine engineering company Harris Pye is to test the gates on the dry dock to see if they are still working.
The investment was made by Kishorn Port Ltd with the backing of Highlands and Islands Enterprise.
Kishorn Port Ltd is a joint venture between Ferguson Transport (Spean Bridge) Ltd and Leiths (Scotland) Ltd.
It is hoped the yard can become a base for decommissioning north sea oil rigs.
Oil and Gas UK has suggested that £17.6bn could be spent on decommissioning on the UK Continental Shelf over the next 10 years.
Some of this work could require deepwater yards.
SNP MP Ian Blackford said the investment aimed to show that Kishorn could be an important player in the offshore market.
He said it was important to make sure Scotland made the right investment to ensure it had yards which were ready to take on decommissioning work.
"It's a pretty unique facility that we've got there in terms of the size of the dock and of course with the high water mark," he said.
"So it's about saying to the outside world that Kishorn is fit for purpose."
Plans to restore a Highlands fabrication yard that operated in the 1970s have moved forward following a £500,000 investment.