According to a BBC report, the contract is valued at around £49m ($63.72m).
The terminal will be designed to support different sectors, including the energy and transport industries.
It will be equipped to accommodate on and offshore wind farm vessels while the main berth will be suitable for the largest cruise liners in order to support the tourism sector.
Additionally, the facility will boost the capabilities and flexibility of the Arnish fabrication yard at Stornoway.
Stornoway Port Authority chair Murdo Murray said: “The deepwater terminal will open a new gateway to the islands for a wide range of sectors and become a catalyst for significant further development here.
“It is already attracting high levels of interest from potential customers. A huge amount of work has already gone into turning this vital development into a reality and we are very grateful to all our partners for their continuing support.
“McLaughlin and Harvey are highly experienced in this kind of work and we look forward to working with them on this project.”
Stornoway Port Authority has been working with the Scottish Government, Highlands and Islands Enterprise (HIE), the Scottish Futures Trust (SFT), and Comhairle Nan Eilean Siar (CnES) for the past four years to advance the project.
Regional development agency HIE has provided funding while CnES has committed a significant loan for the project.
The project work is expected to commence in the upcoming weeks. The initial works will include piling activity, dredging and blasting of rock.