A thermoplastic flame retardant resin composition according to the present invention comprises: (A) about 40.about.95 parts by weight of a styrenic resin; (B) about 5.about.60 parts by weight of a polyphenylene ether, (C) about 0.1.about.40 parts by weight of a rubber modified polystyrene resin containing about 40.about.65% by weight of a rubber and about 0.1.about.8% by weight of acrylonitrile based on 100 parts by weight of the sum of (A) and (B); and (D) about 5 to 30 parts by weight of an aromatic phosphoric acid ester compound based on 100 parts by weight of the sum of (A) and (B).