In this work the fire behaviour of elastomeric panels made of an Ethylene-Propylene Diene Monomer (EPDM) rubber filled with a shape-stabilized paraffin with a melting point of 28 °C and covered with a nitrile-butadiene rubber (NBR) envelope, developed for thermal energy storage applications, was investigated for the first time. The panels were prepared using four different flame retardants (FR) and in order to test their efficacy they were dispersed selectively only in the core material, or in the envelope or in both of them. Cone calorimeter and epiradiateur tests pointed out the efficacy of the clay used for the shape stabilization of paraffin and of the external NBR envelope. Moreover, it was possible to demonstrate that a flame retardant based on ammonium polyphosphate and aluminium diethyl phosphinate could achieve the best fire performances. It was also verified that the combination of the FR both in the core and in the envelope led to the best results thanks to the physico-chemical and chemical interactions between clay, talc, kaolin and silicon with ammonium polyphosphate. The best composition allowed to decrease the peak of the heat release rate (HRR) from 318 kW/m2 to 209 kW/m2 and the MARHE (parameter describing the intensity of the combustion over the whole process of thermal degradation) from 239 kW/m2 to 175 kW/m2. Moreover, regarding the ability to self-extinguish, the number of ignitions at epiradiateur test was increased from 4 to 8 within 5 min and the total combustion time from 391 to 288 s. The improvement of the fire behaviour of EPDM/NBR panels with paraffin makes possible future applications in the field of thermal energy storage of buildings.