Bond Air Services announced last week it had grounded all of its 22 Eurocopter EC135 after a fault was found with fuel indication system on one helicopter in England.
The company said it acted as a "precautionary measure" to ensure the safety of its fleet.
The EC135 was the same model as the police helicopter that crashed into the Clutha pub in Glasgow last month, leaving 10 people dead.
A spokesman from the Scottish Ambulance Service (SAS) said: "The Glasgow-based air ambulance EC135 helicopter returned to service at 7.15pm on Saturday December 14 after being cleared to fly by Bond Air Services."
The other air ambulance within the SAS, based in Inverness, was cleared to fly at 6pm on Thursday.
A statement from Bond Air Services said: "As a precautionary measure, following an issue with the fuel indication system on one of our aircraft we temporarily suspended service operations whilst we undertook further technical investigations of our fleet of EC135s.
"We will continue to work with the manufacturer Eurocopter on any aircraft which are found with this fault, with the aim of resuming normal service as soon as it is safe to do so.
"This is in line with our commitment to the highest standards of safety in all our operations."
Of the 22 helicopters operated by Bond in the UK, 21 are used by emergency services and one is used to service an offshore wind farm.