Video report by ITV Wales' Ian Lang
So far, the company has not confirmed the reasons for the closure but has said customers with bookings will get their money back.
A second park in East Sussex has also shut.
In a statement posted online, the company said: "We regret to inform you that our parks in Prestatyn and Camber Sands will be closing with immediate effect.
"Customers whose bookings will be affected by these closures will be contacted by our team and refunded. We apologise for any inconvenience caused."
There had been speculation the site in Denbighshire could be used to house refugees but a Home Office spokesperson said that was not the plan.
Reacting to the news, Gareth Davies, MS for Vale of Clwyd, posted on social media: "Sad and sudden news of the closure of Pontins in Prestatyn this afternoon, but unsurprising in many ways as they've underinvested for years.
"My thoughts are with the staff, their families and all involved with Pontins Prestatyn at this difficult time."
The holiday park in Prestatyn was built in 1971 but has fallen into decline in recent years, with an average rating of 2.5 stars on TripAdvisor from almost 5,000 reviews.
Pontins is owned by Britannia Hotels, which was rated the UK's worst hotel chain for the 11th year in a row by Which?
The group recorded profits earlier this year despite consistently bad ratings, including a one-star rating for bedrooms, bathrooms and wi-fi quality.
ITV Wales has asked Britannia Hotels for a statement.
Reacting to the closure, a spokesperson from Denbighshire County Council said: “The Council was saddened to hear the news of Prestatyn Sands Holiday Park closing following the decision of the owners, Britannia Hotels. Our thoughts at this time are with the staff and all those affected by the decision.
“The Council has made contact with Britannia Hotels with a view to having an open dialogue to secure the best outcomes for its employees and for the future use of the site.
“It is always sad when a local business closes and this will have an impact on the local community. Working Denbighshire, Denbighshire’s employability and Skills service, will reach out to work with Pontins staff in Prestatyn to offer practical advice, guidance and employability and skills support to help them find suitable, alternative employment or training. They will approach this collaboratively with the DWP, Careers Wales and other key stakeholders with a view to support all staff affected by this development.”
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