This article reports the first example of an inherently flame-retardant PP with self-extinguishing properties, synthesized by incorporating a phosphorus-containing molecular block into the PP molecules via a two-step polymerization approach consisting a propylene coordination polymerization and a subsequent diethyl-(4-vinylbenzyl)phosphonate (DEVBP) atom transfer radical polymerization. A series of polyphosphonate-containing PPs with DEVBP contents ranging from 13.2 to 72.4 wt% were prepared. The polymer structures were confirmed by H-1 NMR spectroscopy, gel permeation chromatography (GPC), differential scanning calorimetry (DSC), and Fourier transform infrared spectroscopy (FTIR). The thermal degradation behaviour of these polymers was examined using thermogravimetric analysis (TGA), and the results showed that the mode of decomposition of the phosphonate-containing PP was different from that of pure PP, giving increased char residue. In the cone calorimeter test (CCT), limited oxygen index (LOI) test, and UL-94 test, the phosphonate-containing PP exhibited improved flame-retardant properties compared to those of PP. (C) 2017 Published by Elsevier Ltd.