Twelve people were arrested for drug offences at the Gottwood festival in Llanfaethlu.
More than 5,000 revellers attended the annual electronic music event on the Carreglwyd estate from Thursday 6th – Friday 10th June.
Six people were arrested on suspicion of drug dealing and six more were held for driving under the influence of drugs.
Meanwhile, a drug amnesty by healthcare volunteers found traces of Crystal MDMA, ketamine and cocaine, along with placebo tablets which contained nothing more than cotton flax and food colouring.
But despite the arrests, officers claimed the policing operation at Gottwood was a success.
Anglesey District Insepector, Laura Davies, said: ‘Our policing operation was focused on minimising the risk of harm to those that attended the event, and to the local community through the flow of drugs into the festival and ensuring the safety of local road users.’
‘The event passed without significant intervention from police…fixed penalty notices were also issued for other minor road traffic offences.’
The amnesty resulted in 227 drugs being put into special bins at the entrance by festival goers, who were also searched by trained staff.
28 officers from the Special Constabulary also assisted officers from both North Wales Police and British Transport Police at Gottwood, by carrying out more than 300 hours of active duty to mark the end of National Volunteers Week.