Officers applied for the closure order after receiving numerous complaints from local residents about anti-social behaviour and drug use at the flat in Maison Dieu Place.
It prohibits anyone except the resident and officials from the housing association who own the property from entering for three months.
Penalties for breaching the order include a fine and up to 51 weeks in prison. A notice has been placed on the door warning that it is an offence to enter.
PC Dannii Rolfe, from Dover’s Community Safety Unit, said: ‘Kent Police does not underestimate the impact that drug dealing and anti-social behaviour can have on the lives of residents and we are tackling the issues with the support of partner agencies.
‘As well as carrying out 36 drug-related warrants in Dover earlier this year, which has seen many drug dealers taken off the streets, we are committed to using every tactic available to us to disrupt and shut down their networks.
‘This order will make it harder for drug dealers to operate in Dover, as well as giving peace of mind to those living nearby.
‘We are grateful for the support shown by both residents and our partner agencies in this case and urge the community to continue to report incidents to us so that we can take action.’