Polypropylene (PP) is one of the most consumed thermoplastics and can achieve wide-ranging properties according to polymerization conditions and by means of additives. For instance, its low fire resistance can be improved with the use of flame-retardants. However, this additive may adversely affect mechanical properties. Within this context different flame-retardant PP copolymer formulations, with and without compatibilizer, have been manufactured. Compounding was performed by means of a co-rotating twin-screw extruder, after which specimens were injection molded and subjected to physical, mechanical and thermal testing, as well as scanning electron microscopy analysis, to identify modifications caused by the flame retardant and compatibilizer. The flame retardant showed to decrease tensile, flexural and impact strength, and increased melt flow rate. In contrast, incorporation of the compatibilizer showed to regain the mechanical properties close to the original values, interfering significantly less with MFR, and promoted minimal change in degradation temperature.