Those who are due to take industrial action work for the Met as call centre staff, recording crime reports and also as technicians and office staff servicing and dispatching vehicles such as police cars and motorbikes.
The 25-hour strike is scheduled to start at 06:00 GMT on 31 December.
Unite said its members voted to take strike action as they have not had a pay increase from the Met for 2025-26, despite the fact the Met has paid a 4.2% pay rise to police officers and all other forces in the UK have given both police officers and staff the 4.2% increase.
It said the Met had put forward two provisional offers: a “below-RPI pay increase” of 3.8% or a 4.2% offer “conditional on workers accepting vastly inferior conditions”.
Last year, policing New Year’s Eve cost the Met almost £2.3m, according to the union.
“As a significant night in policing, strike action will be very disruptive including causing delays to emergency call-outs,” Unite added.