Vodafone has been told that it cannot put up a new mast next to the recycling depot in Hollingdean.
The company applied for planning permission to Brighton and Hove City Council.
But neighbours objected along with Labour ward councillor Jeane Lepper.
She asked councillors on the planning committee to be mindful of health fears, especially as the site, in Upper Hollingdean Road, is a route used by children going to Downs Infant School.
They listened to her plea to “err on the side of caution” and rejected the application.
Councillor Lepper, who represents Hollingdean and Stanmer, told Hollingdean News Online afterwards that Vodafone might well appeal.