Some 4,500 Commonwealth citizens are already employed by the British military, and Minister for the Armed Forces Mark Lancaster said the move will build on the important role Commonwealth countries have served historically.
"As an outward-looking nation, Britain has always counted on the dedicated service of our friends from the Commonwealth to keep this country safe. From Australia to Jamaica, to Fiji and South Africa, Commonwealth recruits are already playing a key role in our Armed Forces," Minister Lancaster said.
The British Army is expecting to hire 1,000 personnel, while the Navy and Air Force will recruit 300 and 50, respectively, per year.
The move also removes the five-year residency in the UK requirement.
All roles and ranks will be available to Commonwealth citizens who are aged 18 or over.
Priority will be given to those who have already applied for Army roles but have been on hold due to limited numbers, with applications beginning in early 2019.
The Royal Navy and the RAF will start their recruitment procedures immediately.