The firm has been operating in the capital since 1876 and the retirement of senior partner Roderick Urquhart will signal the end of its long link to the founding family.
However, the remaining partners have promised there will be no dramatic changes.
Stephen Blane, who will take over as the firm’s senior partner, said: “Roderick is the fourth generation of the Urquhart family to be senior partner here and we want to thank him for everything he has done over many years of service. His will be a very well-deserved retirement.
“For the past 145 years there has been an Urquhart associated with the firm. A number of people have asked us if this is a chance for us to modernise and shake things up.
“There is absolutely no need for that. We are extremely well prepared for Roderick’s departure and the truth is there won’t be any radical changes.
“We will very much continue as we are while keeping an eye on what we can do to improve the already high level of personal service that we offer.”
Preparation for Urquhart’s departure is said to have been underway for 18 months, with a key move being the recruitment of another partner, Alison Grandison, last April.
Based in the city’s Heriot Row, the firm has 24 staff, including ten fee earners.
Of the remaining partners, Gillian Black is the longest-serving, having been with Urquharts for more than 20 years.