GMB members employed by Balfour Beatty Engineering Services Limited (BBESL), Petrofac, and BIS voted overwhelmingly in favour of industrial action, meaning a 24-hour walkout on January 24.
Unite members have also returned an overwhelming majority for action.
The dispute concerns a claim for an additional £50 per day to compensate for the failure to provide suitable accommodation for members and an additional claim for payment for lengthy travelling time undertaken each day.
Workers rejected the offer, which has now been taken off the table by management.
Workers at the Shetland base are constructing a new facility to process the gas and liquid hydrocarbon reserves on a site located to the east of the established Sullom Voe oil terminal on Shetland. Work started in early 2010.
The plant will be connected to the Laggan-Tormore offshore subsea production system. The gas plant is planned to be on stream by mid 2014 and will be operated by Total.
Phil Whitehurst, GMB National Officer, said: "At a mass meeting this afternoon the GMB and Unite members have voted unanimously to reject the management's final offer, which carried the officers recommendation to accept."
Some other workers employed by other contractors on site are also involved in the same dispute, and they will also be balloted for strike action.