The Glasgow firm, one of the main contractors on the athletes' village for the Commonwealth Games, said the agreement would underpin its growth plans over the next three-and-a-half years.
The funding package includes an overdraft, a revolving credit facility and bond facilities.
MacMic, which employs around 230 people, was recently announced as the contractor on the large Shawfair development to the south east of Edinburgh.
As well as the core housebuilding division, it has commercial property interests, timber frame manufacturing and a contracts arm.
Recently, the company has secured Sainsbury's as the flagship tenant of its Thornybank development in Dalkeith, Midlothian, and won a £1.3 m contract from Miller Homes to make timber frames for an Edinburgh housing development.
Ed Monaghan, chief executive, suggested there were some "very positive growth" signs for the business.
He said: "We have been delighted with the excellent support and service offering we've received from RBS over the past eight years.
"We are therefore very pleased to be working with them on this latest refinancing package."
In the 12 months to April 30, 2013, MacMic reported a 44.5 per cent rise in turnover to £55.5m with pre-tax profits increasing from £1.35mto £2.4m.
Stuart Heslop, from RBS, said: "Mactaggart & Mickel is going from strength to strength with a number of prestige projects."