Crandles will assume leadership of the practice while continuing in her current capacity as head of divorce and family law.
She succeeds Ian Clark, who returns to a client-facing partner role after seven years at the helm.
Graeme Gass and Alistair Rushworth, who joined the private client firm on the same day as trainees, have been promoted to partner.
Crandles said it would be “a great honour” to lead Turcan Connell, which has 24 partners and around 200 staff in Edinburgh, Glasgow and London.
She said: “It’s a great honour to take on the role of managing martner and I very much look forward to working with my fellow partners and colleagues as we continue to grow Turcan Connell and meet the exciting challenges of the years ahead.
“Ian Clark hands over the reins of a firm that is performing extremely well and our continuing focus is on maintaining our position as the country’s leading provider of legal services in the tax and succession, land and property, divorce and family and charity sectors.”