Fingal County Council have lifted the "Do Not Swim" notice for Claremont Beach, in Howth, north Co Dublin.
The health and safety caution to members of the public was put in place on Wednesday, after water samples showed a higher than normal level of bacteria in the water.
The Health Service Executive (HSE) advised the local authority to place a prohibition notice on the beach, while further tests were carried out.
The prohibition notice was placed on the beach due to the presence of faecal pollution in the water. Routine sampling of the water found a higher than normal presence of a bacteria called Intestinal Enterococci, which is present in instances of water pollution.
The exact cause of the contamination has not been confirmed, but results of tests taken from water samples on Thursday showed “water quality has returned to satisfactory levels”, according to a spokesman for Fingal county council.
The spokesman said it is suspected the pollution may have been caused by “animals, birds or diffuse surface runoff”.
It is believed the pollutant is not linked to the local wastewater infrastructure.
