Novel brominated styrenic polymers having superior properties rendering them ideally suited for current commercial requirements for use as flame retardants in thermoplastic polymers are described. These properties include such high thermal stabilities in a standard Thermal Stability Test as to dramatically reduce if not eliminate the possibility of corrosion problems due to release of hydrogen halide at elevated polymer processing temperatures. Other special properties of the novel brominated styrenic polymers include, for example, low color or staining properties, and excellent melt flow characteristics.