Scott will oversee Scottish Rugby’s corporate affairs and media operations, alongside 'proactively developing the organisation’s relationships with government, national stakeholders and the member clubs of the Union'.
He begins the new role in August and will report to – and become part of the management team of – Scottish Rugby’s chief operating officer Dominic McKay, who oversees all comms functions at the union.
During a 20-year career in politics, Scott held senior positions including deputy minister for Scottish Parliament; deputy minister for finance, public services and parliamentary business; and minister for transport.
Most recently, the MSP for Shetland has been spokesman for education and sport for the Scottish Liberal Democrat party.
McKay said: "I am delighted to have secured someone of Tavish’s experience to join Scottish Rugby at this exciting time in our development.
"As we continue to further grow our activities across Scotland and internationally, it is key we work hard to maintain the excellent relationships we enjoy with our Government and Local authority partners at all levels whilst enhancing our communications with our member clubs the length and breadth of the country.
"I believe Tavish brings a unique set of skills to this new role which will help us to continue to develop important dialogue and promote the work we are doing to the widest possible audience at home and abroad."
Scott said: "I am absolutely delighted to be joining Scottish Rugby at this incredibly exciting time for the sport in Scotland and across the world.
"To have the opportunity to work for Scottish Rugby is a huge challenge and one that I cannot wait to begin. I will miss the hurly burly of politics and the people I have met and represented for 20 years, but there can be no better new beginning than working for Scottish Rugby.
"Representing the people of Shetland has been my life for 20 years. It has been an enormous privilege and honour to have been Shetland’s MSP since the Scottish Parliament opened in 1999. There have been many highlights, wonderful moments and intense political drama that I would not have missed for anything. So on this, the 20th anniversary week of those momentous events, it is the right time for me to change direction."