It was due to objections made by four nearby residents.
Tayto Park was given the go ahead back in February to begin planning the park's expansion, which would have included the construction of a new €14 million metal rollercoaster, tentatively titled 'Coaster 2021'.
However, An Bord Pleanála have since denied planning permission, in response to objections made by four residents who live in the area.
The four people, who all live less than half a kilometer from Ireland's biggest theme park, made a joint complaint, claiming that the screaming from the passengers on the new rollercoaster would increase noise disturbance in the area.
There was also concern that 'Coaster 2021' would have a negative impact on a nearby EU protected site - the River Nanny Estuary and Shore Special Protection Area - as well as fears that the new proposed development would be at risk of flooding.
'Coaster 2021' would have been one meter shorter than Tayto Park's current high point - the 32 meter tall Cú Chulainn rollercoaster - and it was set to be 972 meters in length.
The new rollercoaster would have provided 40 new full-time and part-time jobs at the park, and in response to the ruling, a statement from Tayto Park said that "the management of Tayto Park is very disappointed to be informed today of the decision by An Bord Pleanála to refuse the planning application for the construction of two new Roller Coasters at Tayto Park".
They are also concerned that if a new attraction is not added soon, then "the longer term viability of the park would be brought into question".
