The new facility will analyse radioactive and other hazardous substances encountered during decommissioning of the most hazardous facilities.
Radioactive analysis is currently carried out in laboratories dating from the 1950s that do not comply with modern standards.
An evaluation of the options concluded it would be more cost-effective to build a new facility than attempt an upgrading of the original facilities.
The new facilities, measuring 1300 sq metres, are expected to cost a total of approximately £9 million.
Site clean-up contractor Dounreay Site Restoration Ltd tendered a contract for design and construction in the Official Journal of the European Union.
Yorkon, part of the Shepherd Group, has been named preferred bidder for the contract, with an approximate value of £7 million.
Sub-contractors include Studsvik and JGC Engineering and Technical Services, which will provide assembly, installation and ventilation services.
Subject to planning and other consents, construction is scheduled to start in March 2012 and take 18 months to complete, with the first analysis of radioactive samples expected in March 2014.
The construction phase is expected to employ 40 people.
The new laboratory will carry out analysis currently conducted in 1950s facilities located in the Fuel Cycle Area. This includes radioactive particles recovered from the marine environment, samples of gaseous and liquid effluent, and noseblows provided by workers at risk of inhaling radiological contamination.
A specialist alkalai metal laboratory currently located in the former turbine hall of the Prototype Fast Reactor will also be relocated.
DSRL employs 45 people in its laboratory service. The old facilities will be decommissioned and demolished.
DSRL laboratory services manager Jeremy Andrew said: “High-quality and efficient laboratory analysis is essential for the safe decommissioning of our remaining high-hazard facilities. The new facility will provide that for the remainder of the clean-up programme.”