Novel phosphorus-containing and nitrogen-containing intumescent flame retardants, bis-aminobenzyl spirocylic pentaerythritol bisphosphonate (BASPB) and arylene-N,N′-bis(2,2-dimethyl-1,3-propanediol phosphoramidate) (ABDPP), were synthesized, and their structures were characterized with Fourier transform infrared spectroscopy and 1H and 31P nuclear magnetic resonance. The phosphorus compounds were used to impart flame retardancy to polycarbonate (PC). Combustion behaviors and thermal degradation properties of the flame-retarded-PC composites were assayed by limiting oxygen index (LOI), vertical burning test (UL-94), cone calorimeter test, and thermogravimetric analysis. PC/5 wt.% BASPB and PC/5 wt.% ABDPP composites passed UL-94 V-0 rating; their LOI values were 35.5% and 34.7%, respectively. Scanning electron microscopy revealed that the char properties had crucial effects on the flame retardancy. The mechanical properties and water resistance of the PC/BASPB and PC/ABDPP composites were also measured. After water resistance test, PC/5 wt.% BASPB and PC/5 wt.% ABDPP composites kept V-0 rating, and the mass loss was only 1.0%. Copyright © 2012 John Wiley & Sons, Ltd.