Novel chlorinated azo phosphazene compounds were synthesized through nucleophilic substitution of hexachlorocyclotriphosphazene with chlorinated azo phenols. Their chemical structures were characterized using FTIR, ¹H NMR, and elemental (CHN) analysis. The compounds were incorporated at concentrations of 1–5 wt% into epoxy, polyurethane primer, and styrene–butadiene rubber (XSBR). Flame-retardant performance was evaluated using the ASTM horizontal burning test by measuring burning time, insulation index, erosion rate, residual weight, flame height, and average burning length. All synthesized phosphazene derivatives significantly improved flame-retardant properties across the tested materials. The compound with the highest chlorine content demonstrated the greatest improvements in burning time, insulation index, erosion rate, and flame propagation resistance. These findings highlight the potential of chlorinated phosphazene derivatives as effective flame-retardant additives for polymer-based construction materials.