Central London firms Gregory Rowcliffe & Milners and Simmonds Church Smiles are merging.
The new 18-partner firm will operate under Gregorys' name.
It will run from Gregorys' Bedford Row premises and Simmonds' Tunbridge Wells office.
Gregorys' managing partner John Anderson says the firm intends to expand its Anglo-German business, which it has built since merging with niche Anglo-German firm Maubie Barry & Scott in 1992.
He says the new firm will retain his practice's managment structure. Anderson will continue to head the new firm and William Bennett, Simmonds' senior partner, will run the Tunbridge Wells operation.
Both firms' London offices are in Bedford Row, and Anderson says the merger was a logical move.
He says: “We have known each other a long time and it seemed a good fit.
“We are literally 10 doors apart and we knew the individuals and we knew that our work type was broadly similar.”
The strengths of both firms lie in litigation, commercial and private client work. Anderson believes that Gregorys will also benefit from Simmonds' expertise in other areas.
Anderson says that the merger is a particularly good fit for the firm's private client work.
He says the Tunbridge Wells office will give the firm a presence in “an excellent area for private client work and we want to expand that work.
“It also brings a strong personal injury element and a much stronger employment law team.”
“The latter is immensely important because of the increased focus on employment law these days”.
The merger will take effect from today (Monday).