The business, which has sites in Glasgow, Stirling and Ayr and is part of Lookers plc, said the move reinforced its long-term commitment north of the Border.
It also noted that under the investment programme it had opened a £3.5m Audi Approved new and used car base in Hamilton, creating 30 jobs.
Lookers Audi group managing director Steve Dean said the firm “has a clear vision in Scotland”.
He added: “In Edinburgh, after several years of growth and building capacity for long-term success, the impact of our investment in a new £1.5m expansion and £500,000 showroom enhancement will be the cementing of our position as the region’s leading specialist in the luxury car market.”
Andy Bruce, chief executive of Lookers, said: “The level of growth, success and ambition seen within Lookers Audi across Scotland is testament to the commitment of the entire team.
"As an integrated, ambitious and forward-looking company, we continue to strengthen our presence in the local marketplace and remain dedicated
to offering the highest quality service provision in Edinburgh, Glasgow, Ayr, Stirling and Hamilton.”
Lookers bought Glasgow-based Lomond Audi in 2012 as part of a £15m acquisition. Lomond Audi Group was first established in 1998 as a single Audi centre in Glasgow. It acquired Edinburgh Audi in 2006 and opened a new dealership in Ayr in 2007.