AbstractEffects related to the simultaneous presence of an Al‐phosphinate based fire retardant and of relatively low amounts of nanosized metal oxide particles on processability and mechanical performances of a commercial polyester resin have been investigated. In more details, ternary poly(buthylene terephtalate) based compounds, obtained by melt processing and first of all validated in terms of flammability, were analysed to verify the relative extrudability and ultimate dynamic mechanical performances of compression moulded samples. Preliminary rheological tests confirmed both a minimum of matrix degradation as a result of the process while applying an appropriate protocol drying of raw materials and a marked reduction of the apparent shear viscosity of the three‐phase melts with respect to the neat matrix processed under the same conditions. Regarding the evaluation of dynamic‐mechanical parameters such as storage modulus, loss modulus and the ratio tan δ, besides the expected stiffening of the matrix by inclusion of a rigid inorganic phase, a slight reduction of damping behaviour without no significant variation of the glass transition temperature of the polyester matrix have been observed.