The Port of Cromarty Firth (PoCF) board announced funding of £30 million towards the expansion, which is expected to be completed by 2020.
The quayside will act as an energy and cruise hub and will be able to accommodate large renewable, decommissioning and oil and gas projects.
It will also be able to berth the biggest cruise ships currently being designed and built.
It will be the second quayside and laydown area to be built by the port in the last three years.
In 2015-16, it invested £25 million in a new 150m quayside and nine acre laydown area.
Bob Buskie, PoCF’s chief executive, said: “This is tremendous news for the port and the Highlands and it represents a significant investment by the board.
“As a trust port, all of our profits are reinvested in the port’s future development.
“We believe this investment will help bring new work to the area for decades to come.
“There is a substantial demand for the services in the port and, even with the large new quayside and laydown area finished in 2016, we still experience capacity issues.
“This new energy and cruise hub will help us resolve these problems and open up the port to being able to accommodate large-scale projects from across all sectors.”
Fergus Ewing, the SNP MSP for Inverness and Nairn, said: “This is excellent news and a result of hard work by the team at PoCF.
“I am delighted they have won this crucial contract and this will provide a real boost to the port and the wider Highland economy.”
The new quayside will be funded jointly by the port and Highlands and Islands Enterprise (HIE), with support from the European Regional Development Fund and commercial lender RBS.
Charlotte Wright, the chief executive of HIE, said she believed the project would benefit other areas in Scotland too.
She said: “We are delighted to be supporting this significant expansion by the Port of Cromarty Firth.
“By strengthening Scotland’s renewable energy supply chain, and creating new opportunities in the tourism sector, we believe this ambitious project will generate wider economic benefits well beyond the inner Moray Firth.”