The flame-retardant efficacy of phosphorus-containing reactive amine hardeners for epoxy resins is well-known; however their synthesis often applies hazardous, objectionable reagents. The aim of this work is to develop an effective synthesis method for the preparation of P-containing amines, which can act as flame-retardant crosslinking agent in epoxy resins. The syntheses and testing of an aliphatic and two aromatic amines are described: curing properties, glass transition temperature, thermal stability, and flame-retardant performance of the amines are studied. On the basis of these results, the scaling-up and the optimization of the synthesis of the phosphorus-containing aliphatic amine hardener in ReactIR™ in situ FTIR apparatus is discussed. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40105.