Four hundred devices have been purchased, at a cost of Â£1.5m.
Body Worn Video Technology, as it's known, is already in place in Derry City and Strabane District.
The cameras are clipped on to the top half of an officer's uniform and can provide eight hours of continuous recording.
Officers have been trained to tell people when they are being recorded.
Supporters of the scheme say the cameras will improve the quality of evidence that police officers can gather.
They will be particularly useful in assisting prosecutions in cases of domestic abuse, for example.
The roll-out follows on from a pilot scheme in Foyle in 2014-15.
Body cameras are routine in other parts of the UK and were first introduced about a decade ago.
Studies have found that they dramatically reduced complaints against officers by members of the public, by up to 93% in one case.
PSNI Chief Supt Chris Noble said: "Video evidence puts the victims of crime first.
"The pilot of this technology in Foyle district evidenced how Body Worn Video has the potential to improve the quality of evidence provided by police officers. It also increases the number of offenders brought to justice.
"The introduction of this new technology is the latest example of our commitment to these principles as we continue to work together with the community to keep people safe."

Forty-two refugees, belonging to five families, were greeted on arrival by the Uruguayan President, Jose Mujica.
They will spend two months in accommodation near the capital Montevideo where they will learn Spanish and  attend classes on local customs.
Other Latin American countries have taken Syrians in but Uruguay is the first to assume all resettlement costs.
Officials say the two-year resettlement programme will cost Uruguay around $3m (Â£1.9m).
They say the adults have already been guaranteed  jobs and the children have places in local school. A second group is due to arrive next year.

The young cranes hatched "in secret" in May - one at the Wildfowl and Wetlands Trust (WWT) at Slimbridge in Gloucestershire and two on farmland on the Somerset Levels.
Experts said, their existence was kept secret to "protect the families".
Conservationists at WWT Slimbridge have been working to re-establish a population in the region for six years.
But this year is the first time birds from the project have successfully reared chicks.
Damon Bridge, of the Great Crane Project, said: "We're delighted - success has always been about seeing birds raised in the wild take flight.
"To have young on the wing in Somerset and at Slimbridge so early on is really fantastic.
"The cranes are long-lived birds with many breeding attempts ahead of them and we are well on our way to our target of 20 breeding pairs in the South West by 2025."
All three chicks have been named Peter in memory of Peter Newbery a "driving force" behind the project, who died before it finished.
Ron and Trish Coombes, who farm on the Somerset Levels, said it had been "very exciting" watching the cranes hatch and rear two of the "three Petes".
They said they were aware the birds were favouring one site but were "astonished" when they appeared with two chicks.
Cranes were commonplace in parts of the West in the 1600s but became extinct across the UK.
A small population has been established in the Norfolk Broads since 1979.
Police officers in Belfast will wear body cameras while on duty from Wednesday.
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A small number of Syrian refugees have arrived in Uruguay from Lebanon.
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Three wild cranes - the first to be bred in the West Country for 400 years - have taken flight.