Abstract: A portable security device adapted to be removably mounted on a door frame adjacent the inside of an inwardly swinging door to prevent the opening of the door and actuate an alarm when forcible entry is attempted. A steel rod is embedded within a rigid housing and extends outwardly from an end wall of the housing. The rod is removably inserted into a complementary-shaped hole in the door frame. The housing has an angled wall extending downwardly toward the rod and forms an exterior angle of between 120.degree. and 165.degree. therebetween. The angled wall lies in abutting relationship with the inside surface of the door blocking the opening of the door. A battery-operated alarm is contained within the housing and has a control button that projects outwardly through a hole in the angled wall and engages the door for actuating an alarm switch. The angled wall may be covered with a sheet of resilient material with the switch button extending a short distance beyond the outer surface of the resilient sheet.