The partnerships of both firms voted in favour of the deal on June 22. The merger will take effect on January 1 next year.
Norton Rose chief executive Peter Martyr will remain in charge of the expanded firm. Deacons Australia chief executive Don Boyd will be deputy chief executive.
Deacons Australia is an associated firm of Deacons, a Hong Kong firm with representative offices in Guangzhou, Shanghai and Beijing and offices or affiliates in Indonesia, Malaysia, Singapore, Taiwan and Thailand. The Hong Kong firm is not involved in the merger.
The arrangements between Deacons Australia and Deacons Hong Kong are expected to come to an end later in the year.