The new wealth giant will be called Tilney Smith & Williamson and is set to be launched in the second half of the year, subject to regulatory approval.
Smith & Williamson employs 1,800 staff and Tilney 1,000 staff.
The promotions, effective from 1 July, cover the Financial Services, Professional Services and Support business arms.
Kevin Stopps, co-chief executive of Smith & Williamson, said: “These promotions to partner and director are well-deserved and recognise the efforts made by our people in helping to deliver an outstanding service to our clients.”
Smith & Williamson and Tilney Group announced earlier this month a revised transaction structure for their proposed merger after the deal stalled during the lockdown. Private equity firm Warburg Pincus injected another £250m to move the deal forward.