A bottle security device locks onto a bottle neck to prevent theft of the bottle or its contents. The device includes a housing and a cap which receives a portion of the bottle neck and rotates relative to the housing. A spiraling cam surface provides a mechanism during rotation of the cap to move a securing member between a secured position to engage the bottle neck and an unsecured position to disengage from the bottle neck. A locking mechanism is provided to prevent rotation of the cap to keep the device locked on the bottle neck.