Improved flame retardant additives are formed from (A) at least one bis(alkanoic acid ester) of a ring-brominated aromatic diester diol; (B) liquid alkylated triphenyl phosphate having an approximate average formula (RxPhO)3P═O) in which each R is, independently, a hydrogen atom or a C14 alkyl group and x is an average number in the range of about 0.2 to 3; and (C) at least one alicyclic phosphonate ester having 1, 2 or 3 phosphorus atoms in the molecule, at least one of which is part of an alicyclic ring system, and having a phosphorus content of at least about 15 wt %. Combinations of these components are well-suited for use in various polymers or resins, especially polyurethanes.