A 20mph speed limit has been introduced outside Rhyl High School to help improve road safety.
Rhyl High School was chosen for the pilot after research at many schools
The pilot scheme will operate during key hours of weekdays in term time and could be extended across the county.
Campaigners, who submitted a 4,000-name petition, wanted the lower speed limit outside all schools in the county.
It comes a week after the British Medical Association (BMA) in Wales called for 20mph zones to be set up along all major walk-to-school routes.
The speed limit on Grange Road, will apply between 0830 to 0915, 1230 to 1400 and 1515 to 1600, Monday to Friday during term time.
Motorists will be made aware of the limit, which covers a 400m stretch, by illuminated signs that flash amber when it is in force.
The speed limit was brought in following a campaign, led by Rhyl councillors Brian Blakeley and Glyn Pickering.
MP Chris Ruane and AM Ann Jones and others became involved and 4,000 residents signed a petition.
Rhyl High School was chosen for the pilot after the council carried out research at various schools, taking into account safety issues such as the speed cars were travelling outside and the number of accidents.
"First on the list we had was schools where there had been accidents and Rhyl High School was top of the list," Mr Blakeley said.
"Over the last five years there had been three children injured outside the school due to traffic."
"There is a tremendous amount of traffic in the morning and evening, people going to and from work. It's also outside Rhyl football ground."
If the pilot scheme is successful, Mr Blakeley said they would be looking to implement more schemes over the next five years.
A council spokesman said the measure was the first of its kind in Denbighshire and believed to be the first in Wales.
Last week the BMA in Wales called on local authorities and the Welsh Assembly Government to identify school routes and introduce 20mph zones.
Such a move, they said, would help tackle childhood obesity by providing exercise and cut road accidents.
John Jenkins, of the BMA in Wales, said the scheme in Rhyl was "excellent news", adding: "We look forward to it being replicated around Wales."