Work at a former bank at 110 Queen Street will create 143,000 sq ft of Grade A offices and 20,000 sq ft of retail space.
The project is being developed and built by BAM and will receive a £9.6m loan from the Scottish Partnership for Regeneration in Urban Centres (SPRUCE) Fund.
Deputy First Minister Nicola Sturgeon said: “Significant city centre developments like today’s £50 million boost for Glasgow are central to stimulating economic growth across Scotland.
“This is absolutely imperative in these tough economic times. It is vital that we support opportunities for new business to help create new jobs and also encourage inward investment to Scotland.
“The transformation of this building, due for completion in 2015, will provide much needed high spec office space for Glasgow, which will enable it to compete more effectively with other large cities – and help to attract companies from across the globe.”
John Burke, Executive Director, BAM Construct UK, said: “This is terrific news for Glasgow and the wider construction sector, and is testament to the confidence investors have that BAM can deliver the largest office development to be built outside of London in a number of years.
“BAM is also investing £40.4m in this project which will generate spin-off economic activity, both short and long term in the construction sector and supply chain as well as a number of new apprenticeships.
“The team is keen to get started and will be moving on site on 7 January.”