Officers from Sussex Police are to march in uniform at the Gay Pride parade in Brighton on Saturday - for the first time.
Uniformed officers joined last year's Gay Pride march in London
Deputy Chief Constable Joe Edwards said the rule had been relaxed for all events attended by the Gay Police Association (GPA).
Sussex officers have to seek permission but Hampshire police have been told they are not allowed to wear uniforms.
Officers were allowed to wear uniforms last year but wore GPA t-shirts.
Sussex Police said it hoped the move would help reflect the large lesbian, gay, bisexual and transgendered (LGBT) community served by the force.
Last year, uniformed officers from across the UK were among 60,000 people to take part in the Gay Pride parade held in London.
Deputy Chief Constable Edwards said he hoped the move would have "a positive impact on the confidence the LGBT community has in Sussex Police".
Sgt Mark Andrews of the GPA said: "Officers marching in uniform... demonstrates that not only do officers police the LGBT community but they are also part of that community themselves and not ashamed to publicly show this."
Forces in the neighbouring counties of Hampshire and Surrey had a mixed response to the invitation by Sussex Police for their officers to join the parade in uniform.
Hampshire Chief Constable Paul Kernaghan said he would not allow off-duty officers to do so.
"It is my view that participation in uniform could undermine the traditional neutrality of the police service," he said.
Surrey Police said that while officers would be allowed to march in uniform, they were discouraged from doing so and would also have to seek permission beforehand.
Officers from Sussex Police will also try to strengthen ties with the LGBT community by running a stand with GPA members at the event.
It is part of an initiative aimed at encouraging people from groups which are normally under represented in the force to apply for jobs.