Dentons has agreed a merger with Scottish firm Maclay Murray & Spens (MMS).
The deal will see Denton's UK headcount increase to 800 fee earners including 200 partners.
MMS currently has offices in Aberdeen, Glasgow, Edinburgh and London.
Formed in 1871 MMS claims to be Scotland's oldest commercial law practice.
The deal is the latest in a string of tie-ups for Dentons which has expanded in Brazil, Georgia, the Netherlands and Peru in recent times.
The deal is set to complete later in 2017.